When I am with a lover, I'm totally focussed on her. The rest of the world can go up in flames. Not just during obvious sex, but in the lead-up & wind-down as well.
I don't want someone f*cking me & launching into chatter about how So-&-So is so great.

And as the "afterglow" seems to have so much emotional vulnerability for so many people, I'd says that's NOT the time to talk about others.
Not that there has to be some minefield about it. Nancy (bisexual) & I had a couple of girlfriends in common. I really enjoy... um, "providing pleasure orally"

; it's the closest thing I have to a fetish. Nancy expressed curiosity about the nuances I had with other women, I was happy to oblige, & she was delighted in various ways.

And I certainly don't mind attempting things that I'd just never considered trying.
But that's all done to ADD TO intimacy.
It's not even about sex, really, but rather respect for who you're with & for your relationship & for your "alone time" together. Anna & I did agree early on that sex is NOT the time to discuss work problems, chores, etc. Intruding on that -- especially recurring -- is disrespectful, maybe even attacking.