The inception could be extensive enough that they led him to believe that he's never met them, I guess. I mean, you did mention that it's easy to completely forget everything they've done 3 layers down. If they actually ended up going to Limbo, then I'm sure they could do that too. The cool thing is that Eames never tumbled into Limbo with Cobb and Ariadne, so there would be no remnants of his Limbo there.

I don't know what I'm saying.