Usually it negotiates up (thats what USB PD is)

Like the device it’s plugged into actually has to communicate and negotiate that it wants something higher.

Until then it’ll just be I think 5V and up to maybe 1amp? (5W)

You did have a phone landline at one point in your life, right?

Your daughter would first have to enumerate and negotiate to switch from 5VDC to 20-48V of USB-PD.

So if she can do that with her mouth, you have other things to worry about. (She’s an android, not some colorful euphemism).

Yes. Power supplies up to 60VDC are typically designed to fall under SELV and are considered intrinsically safe. SELV requires isolation and a single fault tolerant design. Here is some additional info:

https://www.edn.com/what-does-selv-mean-for-power-supplies/

I doubt the USB-C power negotiation feature is specifically a safety function, but as other comments have pointed out it makes the system even safer.

I haven’t looked at the spec, but I wonder if there is any functionality that prevents a power supply from applying 48V all the time. i.e. is it possible to deliver a functional charger that is not SELV and has no power negotiation?

It’s not really the same. The 48VDC of USBC is switched and will be constantly monitored for over or unusual current. A telco doesn’t care and will allow draw to its full potential all the time.