Running backwards to backstab?

Something I have noticed a lot is people running at me with their back exposed.

I know that if I try to attack, I will get backstabbed, but I never really understood why.

I am thinking that the backstab will trigger if they have a heel behind your weapon - is that it? A bit illogical, and a case of bad programming.. Looks silly too.

Now I am wondering how do people even do it? Disengage lock-on?

Lag stab probably, gotta learn to love those things or u become people who complain all day and all night about them lol. Only problem is is that that will never change so u kinda have to deal with it, sucks I know.

yeah i dont get it either

have someones back in front of you, press R1, get stabbed yourself... wtf?

Don't even get me started on this guy that was running at me with a bandits knife doing nothing but circling, and every once in a while he'll warp behind me and I'll get BSed. And then he gives 10 shrugs.