And maybe it's not either or, maybe when you're composing music or thinking about your new book or project you need to be in a creative state and that is very different from a grinding disciplined state that requires you to actually execute on your vision.
But I still hold that you can not ” grind” vision
At that point, you no longer have to grind, because your brain has hardwired decision paths that are automatic and produce correct results for extremely complex problems like "is this character likeable and understandable by the reader", and you can effortlessly add a few high value paragraphs to their backstory. But it's foolhardy to think that level of "flow" can be achieved out of thin air, without writing hundreds of characters before them, re-reading them, getting feedback from other readers, studying other briliant authors with a eye for their technique etc.
That said of course you have to have some level of practice and knowledge about whatever you want to create before you can be inspired to create something new. That doesn't mean you can be creative just because you've had practice. I remember Huberman and others talking about circadian rythms and how people are more creative at night, can't remember the exact reasons, might've been something about cortisol being lower then. I do believe cortisol levels are a hint as usually you are less creative on "uppers" like caffeine or adderall than you are without them because you always want to do things while on them and not actually think deeply about your problem.
Creativity and skill are somewhat orthogonal, you can be an exceptionally well read and educated person yet never publish anything. But it's extremely unlikely you will create anything out of thin air without good technical skills. We like to to obsess about outliers like Beethoven, the deaf composer, but in reality the vast majority of famous musicians are recruited from accomplished instrumentalists.