When resolving Spell Card “Soul Exchange” against an Enneacraft player, I was able to look at the set monsters while tributing them. Once the tribute summon happened, they were no longer visible.
I tried to reproduce it against the AI by setting their monster and then activating Spell Card “Soul Exchange”, but I couldn’t reproduce it, so I’m unsure if it was random occurrence or it only happens online/against Enneacraft (maybe special set monsters?)