DraftKings does it in a way that is good enough to comply with California law, which doesn't require perfection.

This Utah law requires perfection.

I'm not in California and DraftKings blocks me connecting with a VPN, so they just don't seem to be distinguishing whether a VPN user is in California (which is the impossible part of this law).

they want to stop VPN traffic. If it's a plain IP address it's easy. VPN makes it hard.