Ageism is more than a difference in perception. It is a difference in expectations that each of us bring to the candidate journey. It is also the reality that recruiters behave differently when interviewing candidates who have vastly different experience. (I'll leave the "why" behind that for the moment but the facts are not in question.)
Kevin Grossman's post, Ageism in the Candidate Experience, draws on data the TalentBoard has been collecting. On a few questions related to "Fairness" there are very significant differences by age. Bottom line, the older one gets the more one perceives the interview process as unfair.
It might be that every interview is conducted in the exact same way and it's the baggage the older person brings to the interview that colors their perception. Maybe... but no one would believe that covers 100% of the variance. It's certainly something to think about, talk about and perhaps consider digging into a bit deeper.