If i understand how it works correctly, it's not complete/full replay protection. It seems, only BIP 110/BTC2B coin TX with SIGHASH_UNIFIED have replay protection. BIP 110/BTC2B coin TX without SIGHASH_UNIFIED and Bitcoin TX (that doesn't violate BIP 110) are still vulnerable to replay protection. CMIIW.
You're correct and that's how it's supposed to work.
So if you want to sweep, you need to sign your BIP110 txes with SIGHASH_UNIFIED.