But the age gap alone is not a valid reason to complain. The young manager could be in their 30's with over a decade of experience themselves, and they may be highly competent at the work they do. Assuming the young person is not qualified to manage veteran programmers is also a form of age discrimination.
If they're managers they should be in management jobs. If they're not, why should they complain about not being management? Management is its own job, not a "reward" granted for time in service. Not even the military works like that.
The point is that it’s still age discrimination. If someone wants their age to not work against them, they have to be willing to look past the age of others.
Besides age is not an indicator of quality of work, nor are college credentials. I’ve seen much older devs run circles around younger ones, and vice versa.