Im not saying this is nice or positive. Just that it's totally legal and pretty standard.
I know because my first proper employer did NOT put this clause in my contract. Then they tried to introduce it for me and others after adding it for new employees. So I (we, there were 5 of us) actually sought legal advice.
The lawyer was surprised it wasn't in the original contract (and it's been in all the employment contracts I've signed since). Since it wasn't there, they couldn't enforce it or make us sign it. So we were lucky.
Its a hard thing to decide because the alternative is banning this sort of program. Then the only people who get to be pilots are the ones with 130k to spare...