Bingo.
What in this case qualifies as "music theory?" If you label it as any given musical framework (be it microtonality, counterpoint, serialism, etc) then you can ex-post-facto claim that all music ever is based off music theory, and the composers must've thought about it consciously or subconsciously.
Honestly I don't mix both things. To me composing is freeform, you can use whatever you want in whichever way you want.
That means:
Yes you can. You can do whatever you want.
And
Besides the false analogy, it would only begin to make sense when talking is free art and we can say whatever we want. In that context, no you wouldn't be forced to use grammar at all, if you didn't want to.
People have different methods for composing and see things in different ways, let's never forget this.