it still needs to leave at some speed… if the speed was 0 it would just appear at the end of the portal and slide off, which is still not A and it would not reallg leave the portal in the first place.

If you want to view it from a different POV: Imagine you’re at the blue portal seeing the block through there. It would look like it is pushed by the table at the speed the pressure thingy is moving at, as I saod, speed is relative. Sure if it was a teleportation ray it would work like that. I already explained why this would happen.