Okay, i will a few minutes to explain to yo because your statement annoys me. Even I know it and I played tve story last one year ago and still know it.
First you have to understand that the MJ acts in the tree different relatiobshipw differently because he is with three different girls.
Bella ist very secretive, close-minded, difficult to lure out of her shell and still not sure what this thing with MJ is. Do not forget he is a 19-year old frat boy (and not a not man) at college. He will of course interact with hot college girls when he has no clue what to do with this such indifferent, difficult to describe tie with Bella, if it has a future, it lasts long, nor if it is exclusive or official. He naturally will make other girls happy as long Bella keep him starving on her stretched arm. He is caring and patient, but also daring and wont easily waste a chance with other girls. Especially when he is very popular with the ladies.
Next is Sage. Sage is popular, daring, self-conscious, wild, open-minded and a natural-born leader but also caring and supportive girl. With her, MJ acts secure, easy and without second-guessing. Imo he is vibing with Sage the most but that's only a personal statement. Of course it is self-explanatory they are in a mutual loving, exclusive relationship. But he will string some fiddles if he gets offered an instrument to play with as long he does not get caught. MJ is not shy. Thats's for sure if you see him dealing with the strippers. Heck, Sage was even dressed as a slutty high school girl at the Halloween party and hooked up with him on that village stock.
Both women explain his interaction with the ladies. Jill is different as she resemböes more Blla but MJ acts more like with Sage as with Jill if you compare Bella with Jill. She is insecure, inexperienced, tend to be romantic and wants to take things slow. MJ is, i assume, her first boyfriend. As usually he is a trouble-magnet with a soft core as you can see on her rehearsal. He is, naturally, exclusive with her. But he already has done some stuff causing her to interject ciritics. The springlink system incident on Ty's frat party wih the HOTs, him blackmailing Jill with pressing charges to due a non-existent fire, getting in brawling with Chad, Dawe and the Alphas, smashing and egging Ty, running naked in public during Hell Week, burglaring and trashing Ty's room, stealing the deer head and her money and his inability to stay out of trouble. Being with her is time-consuming and needs time to vibe. Those two a natural opposites trying to be together. He cares for her and know how she thinks. No way is deliberately risking something in at least most of the cases. They are not on the same flow/page.
Do you understand know?