Nah, @Dexter I think you mis-understood what I said.
If Predator attacks you out of nowhere and you either parry an attack or you swing with the melee strike — continue to hold that melee button down for half a second then release, the knife 🔪 stays equipped in your hand replacing the gun you were previously holding.
Once you’ve done this it’s much easier to parry and knife attack; additionally, your knife swings do more damage whilst it’s properly equipped in your hand over the quick replace hit that swaps back to gun automatically.