This answer shows that in DFRPG "if you're invoking an aspect on another PC or on a NPC to gain an advantage over them, that character will receive the fate point you spent, either at the end of the exchange (in conflict, see page 197) or at the end of the scene (outside of conflict)." (YS106)
But in Fate Core, "if someone pays a fate point to invoke an aspect attached to your character, you gain their fate point at the end of the scene." (Core81)
Why did Evil Hat change invocation so that Fate points are given out only at the end of a scene?