And your point being what? Listen, yeah I hate metagaming but there are worse things in gaming than metagaming and that is cheating. Nothing is worse than cheating in a role playing game, PnP or Computer/Console. As a game master, if you have to cheat to make an encounter challenging then you have no right being a game master. THe same applies to game designers. Same rules for the PCs and the NPCs, plain and simple.
In one campaign I set up this very elaborate encounter with a main bad guy. It was to be the crowning moment of the campaign, an epic battle that would be remembered for years... In the first round one of the PCs criticaled and killed the main baddie in one hit, battle over.
Did I cheat and make the bugger immune to criticals? No. I let the dice fall where they may and that was that. Same rules apply to the PCs as does to the NPCs.