I never heard that term used for a BBL, that is often what women refer to for breast implants. The buttocks may appear quite swollen for the first 6-8 weeks.
I'm happy to hear that your're happy with your BBL results. Looks like a nice result from the picture you sent. I don't generally use the terms drop and fluff with my BBL patients, although I know some people describe that with breast augmentation surgery as the implants drop. I find that around three months postop we see what are close to final results with BBL. If anything, (and unfortunately it sounds like this is not your hope!) you may see a slight decrease in size as all of the swelling goes away. You may feel like your butt becomes softer and more natural over time, which is part of the "fluff" idea. Don't worry though. The fat is now part of you and will largely remain forever. Best wishes.