I've had this happen to me. For me, I'd say it probably is a validation thing. For the most part, right now I live my life with a fair amount of anxiety; I can never be 100% sure how someone is perceiving me until they make a call by using gendered pronouns (or, alternatively, using 'they,' 'them,' or even 'it' in reference to me).
The anxiety lifts whenever I am referred to with male pronouns or my chosen name. The anxiety actually also lessens if I am referred to with female pronouns. HOWEVER, I believe the anxiety only lessens because I know what that person perceives me as. There's something unsettling about not knowing where you stand with someone. In this case, the anxiety is replaced by frustration because, well, they think I'm a girl--which they can hardly be blamed for, but...

I think I also get what you call the 'shifty-in-the-middle' mode--and that's what causes me all the anxiety.