Earlier quoted context omitted.
Is it? It's discrimination by things that correlate with age, sure, but many things do.
What if instead of discriminating by race, you don't hire people who live in mostly-black neighborhoods?
If you explicitly don't accept applicants only from select neightborhoods that all just "happen to" be almost all-black, you're still discriminating by race and it's still obvious and obviously illegal. You'll just waste more of everyone's time in court.
Just look at sovereign citizens and their inane shenanigans like "I'm not driving, I'm traveling by car and therefore don't need a driver's license and can ignore speed limits".