BCH was a clean hard fork. There was no wipeout risk for the BTC chain if the BCH chain became longer. BIP110 is a chain divergence and BIP110 chain coins are valid on the legacy chain, but the opposite isn’t true. In theory the BIP110 can exist for months or years along the legacy chain, and presuming blocks are still added on the bip110 chain, the longer this divergence persists, the higher the risk of wipeout becomes for the legacy chain.