While I don't know about those two characters in particular, the sidequest characters now show up in Sunport, or some other area instead. I wonder if those two have a post-quest location.

While I also initially missed catching up with the side quest characters at the end-of-main-quest afterparty, I much prefer them having their own location.

This way, you can do the sidequests whenever you want and not worry about missing content or updates on the characters because you finished the main quest before the side quests. I sorta hope this becomes the new direction and that it's announced officially.