Unfortunately due to the damage to the camera lens they would possibly contribute the current issue to a drop. i.e. user caused.
I appreciate from your viewpoint this wouldn't be the case and two separate issues.
Also they'd probably need to get into the phone to test its internals which currently the cracked lens would cause an issue and wouldn't probably withstand the procedure hence it would be a chargeable repair.
In the UK some people have standalone phone insurance or like me have household insurance that covers phones. Some bank accounts cover phones too as a perk of the account.