6 Hour is too much of time to waste life. It should be 3-4 hours max. 6 hours is something every kid have after the school. 3pm-9pm. If they give that to the PUBG, they are left with hardly 1-2 hour of study only which includes coaching.
I would say, ask them to play PUBG PC. They will have no addiction left to PUBG. PUBG Mobile, even an old grandpa can play.