It doesn't really make sense:
1. We will be crediting users who had BTC in their account balance at the time of the fork with matching BCH.
2. We have not yet determined if we will be listing BCH as a market on Poloniex nor can we commit to supporting BCH withdrawals right away.
If I get BCH but can't trade it (on a trading platform..) and can't withdraw it (on a trading platform..) then what can I do with my BCH?
I assume it means they will EVENTUALLY decide to either allow both trade and withdrawals or they will allow only withdrawals. How long it will be before they decide is unknown but the point to make is they aren't just keeping peoples coins for themselves.