[ludable]

I want to add something to my snappy answer. Age discrimination is just another facet of lack of diversity and rejection of difference that plagues many industries.

Your well-intentioned comment has the pattern:

"I've worked with some extremely smart <class of people>, who <positive comment>. My impression is that usually, in my experience, <display a different pattern of thinking to what I expect>. They also seem to usually not go out to happy hours/events with the team to get to know one another as often, so they're excluded a little more, which leads to fewer people getting to know them.

It's just that most of the <class of people> I have personally met seem to have the traits I described above. This would give me a little pause when choosing between equal candidates for, say, an angular dev position where both candidates have equal experience in the stack, but the <class of people> one has the baggage(?) of <difference>. I would likely have an unconscious bias to hire the <more similar to the norm> one."

Now, replace <class of people> with "women" or "muslims" and think about how it feels for people to be cast in a generalization. If it's not right in those cases, it's not right for experienced developers either.