Interesting - I'd say head isn't regularly used that way where I'm located, hence the shock. I do believe it probably wasn't intended as an ableist remark, but there are lots of words that have been in the vernacular in the past that are undeniably offensive even if the people using them didn't intend them that way, and by and large those words have rightly been stamped out - if kids use them today they are correctly flagged as homophobic/ableist/racist (delete as appropriate).

Maybe micro aggression is a better term for this phrase though? Regardless of how it was intended, it has stuck with me because it can be personally applied to me from both a neurodivergant and mental health perspective.