I am personally not fan
One thing about Champion virginity scenes (aside from whether writers have an interest in doing them in the first place) is the return on time investment. Unless they're roleplaying it for a specific reason (like I am with one Champ waiting for Ryn's cage to come off) the vast majority of players are likely to lose all their relevant virginities early on, so the further into the game you have to go to see any particular scene, the less likely it is that there will be players in a position to see it and so the less sense it makes to account for it. Some writers might because they're into it, others won't.
Meanwhile very few of the companions are virgins so there's not much there to write about. I think Ryn is the only one who hasn't had real sex of some sort before meeting the Champ and Cait is the only one who has something they haven't done that's treated as a Big Deal. Okay, there's also Brienne, who's a virgin as Brienne but she's a pretty unusual case. Maybe Einen will be based on what we've seen, but that's in the future. So aside from Brienne, Ryn's first time getting to use her penis and Cait's anal scenes that were just added, there isn't much there to hang a scene on.
Actually, a lot of our companions do have virginal elements to them.
I think both Brint and Quint (if I remember right) are anal virgins along with Cait. I at least think so, since unlike Cait, they do not make a big deal out of it. Brint comments on how he never had more than a finger near his donut. And Quint, by Bubsies admission, only pitches so I assume he never tried it. Also going by his riming scene, I guess that is the case. Or, maybe his GF pegged him and he is ashamed to admit it. Now, unlike Cait, I do not think they make big deal out of it so no real point of writing it.
Brienne, as you said is a special case. She is basically entirely new character so she was a virgin in a few aspects. But even than, there was no real point of dwelling on it considering she has few things in common with Brint.
Ryn was basically confirmed by the way that her sister treated her. She was saving Ryns dick for there weeding night. She can go either way. I just hope that we are not forced to take her dick.
Einen is a virgin by Williams admisio do there is that. Again, I am assuming a lot of her, but considering what William wrote, there is going to be a process of breaking her in.
And finally Berwyn, with his new expansion and possibility of gaining a cunt he will be a virgin there. Again who knows.
But yeah, at the end of the day, taking someone virginity is not something I really pay attention to. Only time I really enjoy doing it is in fetishistic genderbend situations (ftm or mtf or gaining dick/vagina) since it is basically introducing the person to new sensations.