No idea how big this backlash was but it's not like I can't understand it, bigger isn't always better and I never liked when artists inflate girls either, particularly in cases like Suisei's where her breast size seems to have become an established charm point for the fanbase from what I've seen. That said I wouldn't lose my mind over it, just ignore it if you don't like it.
If you're getting "possibly due to backlash from replies" from that tweet, that's a mistranslation. It's apologizing to everyone that took the time to reply to the art (since they get deleted along with the art). At face value, the artist deleted it out of their own volition.
