I can't speak specifically to this case, but it's certainly not about saving KB, it's usually specifically to prevent people from messaging the same person multiple times a year for many months/years.
IIRC, OkC also removed the ability to bookmark profiles, presumably for the same reason -- everything moving to a more "ephermeral" experience to prevent anybody getting "obsessed" with certain accounts because of how creepy that gets. Since spam, stalking, and abusive messages are by far the #1 problem with any online dating service. (Yes blocking works, but it's even better when people don't have to block in the first place. If you have to block too much, you quit the app.)