I see what you're saying, Kat. Mind you, if you tell a new writer to forget grammar, forget spelling and to forget that a plot is a series of events that are somehow connected... I can't see how that's good advice and I can't see that this is the advice that any of the writing advice in this thread has been pushing.
That wasn't my advice. What I'm doing is stating simple fact -- there is not one grammar set. What "grammar" you use depends on where you live, what school programs you had where you live, your reading and communication experiences, when you were born, etc. We use different grammars when we talk and when we talk with different groups of people, when we write different things, and the grammar that someone communicates back to us may be different from the grammar we used with them and grammar conventions wherever we are continually change. Grammar -- structure in language -- is NOT set or singular. It isn't a set of rules. It's styles of using language. And all of those styles are valid because people use them and use them in fiction as creative expression. And the people who use them don't necessarily know "rules" of grammar, the conventions of a particular set -- they use language in certain ways that employ types of grammar. And readers understand them perfectly fine.
Which is why I don't tell people that they should "forget" grammar because they will use grammar -- a grammar in fiction usually with sentence fragments in it as part of that grammar. I tell them there aren't a one set of "rules," one grammar set that they must know and follow and worry about. Fiction writers do not use all the same grammar sets. And depending on the country, they don't use the same spelling for words a lot of the time.
As far as the made-up languages -- I think that would mostly sit in the dialogue spoken by characters... or as a fixed feature of the created world... if a "blarn" (for example) is the word the writer uses for "brick" a blarn remains a brick throughout the story... if it was truly random... and a blarn could be brick, a slice of bacon and a motorcar while at the same time not being a brick... (unless it was explicitly stated that a blarn could be anything or nothing) I'm doubtful an audience could follow the blarn's character too easily.
Cognitively most readers will do just fine with it. See "I am Groot." Some may find it confusing, but some readers will always find any fictional text confusing, even if authors put in explicit instructions.
Overall though I'd say that while writers may choose the rules that they'll apply or not apply for creative reasons...
Whose rules are they choosing from? There is not one authority issuing one set of "rules." Again, you're using the word "rules," but you're talking about styles.
I think it actually helps in order for the novice writer to see what it is exactly that their favourite authors are doing differently.
Differently from what? Again, there is no standard that writers either follow or move away from. There are different stylistic approaches that different writers use for everything from sentence structure to chronology. None of them are more standard and rule-following than the others. That's the problem; the use of the word "rules" sets up an imaginary world where there is a standard set of rules for writing fiction. And there isn't any. What people trot out as rules are their own stylistic preferences, stuff about writing they've heard of or read that they think personally makes sense to them and they like and use in their writing. And when it is pointed out that this writer and that writer aren't following those stylistic preferences, inevitably that's just those writers "breaking" the supposed rules. Apparently the "rules" only exist for writers to break them, which means that whichever "rules" you're pushing as "the rules," they are rather useless.
Further, some writers get told one set of rules and other writers get told another set of rules -- which sometimes contradict. So are all those writers then ignorant of the rules, and doomed to be supposedly poor novices forever because they don't know all the rules that anyone has ever made up about fiction writing and can then break them? Rules is a useless word in fiction writing because
there is no one issuing any rules. Nor any penalties for not following imaginary rules. Nor any particular reward for being a rebel who "breaks" imaginary rules. There are just a lot of stylistic choices that authors make, with a few being more commonly made than others. Which does not make them rules, just popular with authors.
Also, you spelled favorite wrong. Oh wait, no you didn't, because in some countries, favorite is spelled favourite. How will someone in a different country ever understand the word if it isn't spelled according to their "rules"? It's amazing that I understood what you said.
The reason I started this thread topic is that writers think, since they get told that there are rules to writing fiction, that there is also the rule of only one way to do the writing process. Some people actually tell them that there is only one right way to do the writing process and they think those people know what they are talking about. And if that one way that they think is the rule of the right writing process doesn't happen to mesh with their own actual writing process, it messes them up. And also, writers tend to have to figure out their own writing process and hearing about what other authors do can then sometimes give them ideas to try, some of which may work for them or not. The idea is to show that
there aren't any rules to the fiction writing process, just choices, by showing the actual facts of what writers are doing. (Plus it's just sometimes interesting to hear about.)