More than every game if not every game I play in Just Build: Duos I see certain players going AFK I think probably to save themselves a ridiculous amount of time to gain EXP or rewards you could get in the game. Let alone two players, one will be building meanwhile the other is AFK so that’s pretty obvious they did nothing but get the same rewards as the player who built and put in effort to their builds.
My suggestion to this problem is if they do not move or rather place a block within one (1)or so minute(s) in the game, they should be kicked out.