I knew there wouldn't be fog of war, but they could also see (possibly, no clue how the game works) amount of resources left which i guess a person could count anyway... but also cooldowns on special moves, which special moves someone opted for, or who knows what else.
I guess most of these things could be counted if there is a replay feature. Sitting around with friends playing on a couch is quite a bit different than playing online. I'm not sure how many people would bother watching replays if they had full vision and were playing with friends in the same room. Some people might be able to remember when their opponent made a certain move but I sure can't haha.
I guess you are right though if they have full vision and know what someone can do, then there really are no secrets except the plan inside someone's head.