As far I’m concerned, it’s LGBTQIA+ slang. Why would you use top/bottom in a BDSM way, when the words dom/sub exist?
See also the popular introductory BDSM books “The New Topping Book” (2003) and “The New Bottoming Book” (2001) by Easton and Hardy. Both are queer but use topping and bottoming regardless of gender for dom/sub. So I wouldn’t even say it’s a new phenomenon.
Edit: Judging from the sidebar and the posts so far I assume it’s meant in the LGBTQIA+ way, but would be a nice improvement for the sidebar to clarify. :)
Yes
It’s not specified, but I imagine it would be called submissive rather than bottom if that were the intent.