Just to be clear because I think I phrased my reply poorly.
Seeing the cards in the opponent's hand/discard/banish is intentional and totally fine. Seeing the "face-down" card the opponent has in play before you choose your play would be a bug. Whatever card they played should show as in the opponent's hand until it's revealed when card resolutions start happening.
Some might happen later in the turn after card reveals (Radiant Black ult, Griffin passive) but they're still after your card was played.
With the characters on BGA, seeing their hand offers no gameplay advantage since it can deduced with perfect accuracy from what's face-up in discard/banished/stored. It just makes it more convenient and new player friendly.
But definitely submit a bug to the devs if you're seeing the opponent's played card before you have to choose yours (screenshots/video would be super helpful to them I'm sure).