I find it hilarious how you will "voluntarily" enter your phone number or email into their service to check if it already exists! I might be paranoid, but what

I find it hilarious how you will "voluntarily" enter your phone number or email into their service to check if it already exists! I might be paranoid, but what prevents FB from storing this new data if it is not already there?! I think this sort of behavior should be clearly articulated in the next update of the GDPR if it is not already addressed.