Ageism does occur in this industry, but I've mostly heard it around associating various levels with age or years of experience. For instance, at a financial product company I worked for I saw a man who went on to become a Googler get cut from our interview because he "had too much experience to be a senior". For context, most of his background had been in contracting and he'd only recently really invested himself in DS&A knowledge (the kind larger firms look for). The kind of companies he had worked for put his skills cumulatively around Senior but he'd been in the industry a long time.

There's "innocent sounding" explanation for the managers decision to cut the interview, but they're all tainted with some form of ageism.