"Fragile high self-esteem" is the same thing. Overachievers are generally effeminate nerds. We are also ultimately not rational creatures and can enjoy / seek out things we may consciously reject, especially internally. Certainly not an attention whore though.
I say this only because of experience with this kind of response and behaviour. Anecdotally, such people do indeed rate their abilities very highly, they just don't brag about them (often introverted as well). They think they are better than most people, but this is shadowed by a sense of inferiority (physical or otherwise). They delight in praise even if they are torn between embarrassment and delight. This is why I call this behaviour womanly. Such people are always restricted to second tier and frustrated because they are not truly comfortable in themselves. Perhaps I am totally off, but Corpse is the only judge.
Downplaying one's ability (among other things) can be a social cue instead of simple information exchange, an appearance more than a conviction. We are such social creatures that one can easily convince themselves of conviction where only appearance exists. Status signaling goes hand-in-hand with human existence. It is valuable to recognize it, everyone is afflicted.