This is your threefold reminder:
Hakarane is real and constant.
Hakari may be a different type but she's just as tsundere as Karane (or her)
The majority of the girls in the RenFam are bi so we've just witnessed the birth of a new ship. RiNemu.
Are
most Bi? There are certainly some that are or might become, but
most seems a stretch.
I guess to be in such a polygamous situation there could end up being more of it, but as this is a divine cause it doesn't necessarily change their prior preferences.
I don't have a problem with most, or all, being bi, I just haven't felt that its that widespread among all of them. Enjoying each others company as they do in this family does comes across as dating in a lot of ways, but most of them don't feel like sexual attraction. Even when they all enjoying kissing Rentarou in groups doesn't make them more bi by doing it alongside the other girls as well. Even the ones that are pretty overtly bi still have Rentarou as their main focal point rather than each other.
Maybe with an empirical study of all the girls interactions a more accurate value could be reached, but on my gut feeling at the moment I'd say even a third of the girls being actually bi, rather than just polygamous acceptance with the other girls, would be a generous amount.