If a card is revealed and put on top of deck (not shuffled), the opponent already knows what card it is. Also note this is the case for all ygopro simulators that when you add a card from deck to hand, it is revealed until you shuffle the hand. In our sim, the hand is auto shuffled for this reason.
In Duel Links, they also have a log. If a card is revealed already, then it will be in the log. Visually, hence, it won’t matter if you block or not since the log is there. This is also the same case for face-down monsters that were already revealed.