Not surprising. Years ago one of my (gray haired) mentors opened my eyes to ageism in this industry by asking me to pay attention to how many programmers in the office have gray hair. Once you start looking for it, it becomes obvious that age discrimination is rampant. Some blame the young workforce on the industry being young, but the industry is decades old at this point so I don't think that excuse holds water.
The second nuance is that I and the rest of Gen-X sit one the cusp of the desktop revolution and its transition to the internet revolution. Most of the desktop programmers 30+ year at that time, did not make the transition, they stuck with desktop and rode it into the twilight of their career and that is a big reason you just don't seem to see too many people over their mid 40's in the industry.
None of that negates the fact that ageism does exist in this industry, but there are other contributing factors as to why we don't see many programmers past the 40's cut off.