I don't know about this policy on BC.Game but years ago, I did read a similar term of account deactivation by Poloniex exchange in their ToS. I did not know any Poloniex users got their account deactivations by Poloniex but at least the exchange ToS shows this is possibility and risk of inactive accounts.

I did not know other centralized exchanges or online gambling sites have that similar term like Poloniex and like you, I glad to follow it up from this discussion with more details on this term at BC.Game. If the term is truly applicable by BC.Game, their users must be careful and if they plan to be inactive for a long time, they need to withdraw their money from accounts, just in case.