At least with Shrek (at the time) they didn't own it, and were probably happy just to have a top IP of the time. Still, I think it gets a pass because it takes place at a specific time and doesn't alter any of the dynamic between the characters. With Fast, we're changing the interactions of the characters.
Also, just remembered a spin-off was announced so maybe spoilers aren't necessary?
But yea, since they are filming new scenes, and I'm sure they have some inside as to what was going to happen, there is no reason we shouldn't see a change of some aspects; especially since it seems we have a major baddie for a bit.