I agree (having only read the article, not the study) - I think the overall premise that improvement in a skill is incompatible with ego reduction is simplistic. You can absolutely improve on something overall while perhaps regressing on some small part (Simpson's Paradox). It's like saying that no-one can be truly humble if they believe (but not brag!) they're more humble than average - they're probably just right about that and can still be an unassuming person all around.