They were making a joke playing off imposter syndrome. The best way to explain it is through example: let’s say I’m a successful CEO but I still look in the mirror and see my teenage self that made lots of mistakes and I think everyone else sees me the same way. So even though I AM a CEO factually and I do my job well enough to have it, I feel like an imposter because I feel too stupid to have it, unworthy, etc.

I think almost everyone has some form of imposter syndrome especially when people around you don’t treat you the way that you should be (like a mother over babying their adult child or something)