You nailed it! A "tradition" slur of the Japanese has been to accuse them of being "slippery", "deceitful", and "lying". Apparently, the slur originated in early Western misunderstandings of the Japanese cultural view that a person, in effect, has multiple identities or selves. Japanese scholars and apologists often responded to the slur by making the very same point that you have: That even Westerners adopt a different attitude with their peers than they do with their parents. I gather, however, that the Japanese are much more thorough and profound in that regard than Westerners.
By the way, I once witnessed a Japanese woman transform herself from a traditional, very demure and shy Japanese lady to an upbeat, energetic, and quite personable Western woman. She was the translator for a group of businessmen. As long as she was in the company of the men, she behaved exactly like a Japanese lady. She kept her eyes downcast, spoke in the customary manner of a Japanese lady (that is, she spoke as if she was breathless), and so on. Despite the fact that I was at the time married to a Japanese woman, and knew a little bit about the culture, I was still fooled: I thought I was seeing the "true her" -- as if that's all she was.
But almost as soon as the men left, she got up, crossed the room, and was at once indistinguishable from an outgoing, extroverted American college student. The whole transformation occurred within her walking twenty feet.