I think Ocean will give us future 'outs' for each of the LI paths that the MC can choose.
I don't think it is a forgone conclusion that Bella and the MC Must break up - only that he will have the choice to break up with her to pursue another LI - and/or he will have the choice to break her trust - lie to her - to be with another woman and there will be consequences.
For ex: In CH 5, my MC had the choice to tell Bella that I kissed Vic and be up front about it or say nothing.
I chose to tell her but choosing not to could easily lead to future drama in season 2, and rightfully so.
You don't have your first serious discussion about trust and honesty only to lie by omission shortly after the end of that convo.
Ocean already said that there would be relationship drama in any throuple (I believe that this was from Discord convo's) even if it occurs because both women want the MC to spend time with them and he cannot be on two places at once, so he must choose.
We will have to see if keeping a throuple going is a choice based balancing act that can fail if one woman is shown too much favor over the other woman in the throuple.
Cheers!!