No, metagaming is acting on out-of-character knowledge, and if you think about it, that's exactly what's being advocated by those who insist a character be roleplayed according to its scores. A character can't possibly know what its intelligence score is, so to make stupid decisions for your character based on the OOC knowledge that the character has an Intelligence of 5 is metagaming. In my experience, less intelligent people are actually far less likely to be aware of their own cognitive limitations than a more intelligent person. Unintelligent people don't think, "I'm not very bright, so I'm going to choose to do something stupid." No, they actually choose what seems to them to be the best course of action available. That's what it means to play the role of that person.