Just accept the heal. Maybe they need it for a perk, maybe they want the points, either way it doesn't matter their reasoning. If someone approaches me while I'm healing with a medkit, I'm not gonna say no.
I agree with the OP people don't understand two people stuck doing an action is so much worse than one person doing the action while the other does a gen. If I want a heal I'll ask for it otherwise let me use my gd medkit I brought it for a reason.