Uber lets you enable a PIN for each ride. The driver can't say they picked you up until they punch in the random 4 digit PIN the app gave you for the ride.
It's not unusual to call a taxi for another person. Or to make a multi-stop journey where some people get out before others. You can even send a parcel across town in a taxi.
Checking phone proximity might be helpful in some cases, but it's not a silver bullet.
I never give location permissions to any app if I can avoid it (indeed I don't even have the spyware app if I can avoid it; e.g. I use the web to order an Uber)
Exactly - I believe it should be required for safety, limits shenanigans, etc. Apparently, it is required in Puerto Rico, but I don't know if drivers have to enable it themselves or if the app knows where the driver is operating. Are you saying the rider can also turn it on all the time? If so, that's good - I've only ever it seen driver's request it (all in PR, and one in mainland US, everywhere else, no PIN).