1. Player A and B are both using grippy inverted. Player A gives good topspin and player B blocks. Player B's rubber grabbed the ball and it returned with topspin. The spin changed and therefore stayed topspin.
2. Player A is using grippy inverted and player B is using long pips or anti without any friction at all. Player A gives good topspin and player B blocks. Player B's rubber did not grab the ball and the same rotation continued back to player A, which is now backspin.