Wouldn't your experience be at least as likely to mean that you are simply in the 29% of people who cannot do this? I would imagine people who can't flare their nostrils, roll their tongue, move their scalp (maybe this one is just me), or any number of other common but not universal movements would feel the same way you do at being told that these movements are not only possible, but quite common.

I'm no trained observer, but looking at myself in a mirror right now, I can fake a smile that appears to me no different from a genuine smile formed while focusing on a happy thought. But I don't think I have a very expressive face in general, in addition to now knowing any key things to look for other than crows feet.