Maybe they think Discord will provide an example of proper corporate behavior, so they'll have answers for the "but we have to make money somehow!" and "everybody's doing it!" canards.

I am also curious why they decided to also include discord considering so far there monetization strategies so far has been to sell stuff to users, instead of sell their uses.

I would imagine it's at least partially because Discord skews pretty young, with a large audience of minors.

I'm also a bit surprised about the inclusion of Discord here. Not only is their monetization different, but their daily userbase is pretty small compared to the rest of the list (I believe Reddit would be closest).

It makes me wonder if there are some concerns about what Discord is collecting/using in particular.

My totally unsubstantiated gut feeling is that they might suspect that Discord harbors more "radicalizing" potential, compared to other social networks. Probably because discord servers are private, self-moderated, and demographically very skewed towards young men (since it's commonly used for gaming chats). I know that some of the more "troublesome" subreddits use discord to discuss sensitive topics without worrying about reddit admin censorship, so communities like those could be causing a bit of FUD around Discord as a whole.