That kissing couple is definitely Matthew (Bianca's guy) and Olivia (Andy's girl) from Jill's group of friends.
Everyone's so focused on Quinn and the mc in that park bench scene, they ignore the identities of the PDA couple (or the fact that the Jill and Quinn paths are mostly mutually exclusive and people haven't seen everything on both sides of the DIK/Chick coin).
Not sure if DPC just re-used their models, or it's a definite plot twist, but you gotta be pretty stupid to be kissing a friend's wife/husband in public like that...