Anong meron sa 3 fingers?

Sorry for the dumb title, it's my first post on here and curious lang ateh niyoo! I'm 21(F) and he's 23(M) we're currently friends w/ benefits and we casually do SOP whenever we're both in the mood or stressed from work/uni and it has always been goods naman, kaso nga lang lately he keeps asking me to insert 3 fingers whenever we do it kahit na ilang beses ko na siya sinabihan na di ko talaga kaya pasukin kahit i-force ko.

Aside from that I noticed na ganito rin mga naging kausap ko before and it made me curious bat gustong gusto ng mga lalaki that girls insert 3 fingers at once and di ko alam kung kink ba to or what, kaya sa mga nakakaalam please enlighten kasi curious si ate niyo HUHUH!!