I don’t think that right now anyone would upload an item which is considered unfinished even by themselves at the time. That just doesn’t make any sense. But if there were an option to update your files while in the review queue, that would lead to chaos for sure. Lots of authors would toss their “dummy” files in the queue to save some time and only finish the job while the “item” is waiting for review.
I think what #RimoMusic says is legit, and if it was a problem for the review team they would not allow it. It’s for the sake of better quality and it’s in their interest as well to provide top notch items for the buyers.