There is no such thing as an over the back call or a reaching in call if the defender doesn't make contact. Everyone knows that. When you jump into someone's back and push them forward to get a rebound from behind them, that is absolutely a foul and people call it "over the back".
When you reach in and don't make contact, it's not a foul. Everyone also knows that. But when you reach in and make contact, it's a foul. People call it a "reach in".
I see people all the time say there is no such thing as an over the back or a reach in. Since you just said it, can I ask you why? Do you think people don't understand that it's not a foul if you don't make contact? Or do you just hate the naming of the fouls? Would you rather someone say "he jumped up and bumped him from behind when he was trying to get that rebound!"? Because to me it's just easier to say "over the back" since everyone knows what that means anyway.
Or is it just people trying to sound smart because they think they know something about basketball that other people don't?