From a switch's point of view:

Not being a huge fan of checklists and announcing all of my kinks in advance, in my experience, topping from the bottom happens most often when during play, my partner is dominating and he is very close to doing something I like I will ask (not beg) nicely that he do that or this...I find it to be a good way to teach him what I like, and he does it back to me as well...

Maybe it is a switch thing, it seems a useful way to learn more about what your partner likes...giving my partner pleasure is extremely important to me, and if he wants to please me (and he does) I would be remiss in not topping from the bottom on occasion...not only does it let him know what I like, it reinforces that I am consenting.

In have been pleasantly surprised by some of his requests and I know he has had the same pleasure...it is part of unwraveling the unknown and can be fun for both!

I am not offended by the phrase, it is an accurate description of something that does happen.