In preparation for author rebuttal for a conference, we have conducted additional experiments and significantly improved our paper already (of course the reviewers can’t see this yet, we may mention it during author rebuttal if the changes relate to any of their comments).

I’m wondering if this is an issue and does the final version of the paper have to be very close to the initial submission, and only improve upon what the reviewers mention? Or can we add other improvements as long as they are high quality and don’t detract from the original submission?