Just my two cents!
Woohoo partners are basically "friendships with benefits". Many adults who are a part of the hookup culture do not kiss because it can often have a romantic connotation or at least become a concern that the hookup could lead to more than just sex, especially among those who aren't looking for anything serious in a society where kissing is more often than not thought of as romantic. Not everyone thinks that way, but that is what I have noticed from reading and talking to other adults about it. EA probably wanted to simulate something similar, hence the feature's execution. Making out is actually common between friends with benefits, so I'm surprised that wasn't included. I can understand a tender kiss on the cheek, but making out could've at least been added.
Nevertheless, the new woohoo partners feature seems like an adult thing to add, so I'm not surprised some Simmers are confused. Despite the T rating, The Sims 4 has been heavily marketed to a younger audience compared to the original game from 2000 that was more adult in humor and tone, so while I personally welcome it, I can totally understand the mixed reaction. I mean, woohoo in TS1 (play in bed) had the Sims remove their clothes before performing the interaction, and TS2 had the goose interaction, so the franchise has definitely gotten more "youthful" so to speak.
I hope this helps!