Playing football is a very physical activity so clearly some consideration of age, and height-weight, is sensible.
But if you're a pilot, then so long as you can maintain a class 1 medical, what difference does it make if you're big, short, not within some arbitrary age range, etc etc?
I've never heard anyone object to discrimination based on merit or aptitude but some of the things that airline selectors appear to be getting away with are ridiculous. Just look at the lack of diversity for the evidence.