I suppose the key question is: Does it identify the device and then decide not to work with non-Dell devices? It's fine to read required information, but unnecessarily constraining what happens based on that information brings it back to DRM.

The power supply is "constant current, constant voltage" - ie. it is 19 volts for all currents under 3 amps, but if you try to exceed 3 amps, it will supply exactly 3 amps at whatever voltage that works out to.

The benefit of this scheme is it's super easy to implement on both sides, and fully universal - the device just keeps increasing the current draw till the voltage starts to drop, and it then knows it's hit the limit. The device doesn't need any kind of logic at all - a dumb light bulb will either work if there is enough power, or not work if there isn't, but nothing will get damaged.

It's also compatible with Y splitters - so you can plug in two laptops to the supply, with no extra electronics, and both can share the power. (there is no guarantee of even power splitting tho!)

A big benefit is the power supply can have fully variable capabilities - for example, most power supplies are thermal limited, and on a cold day it could offer slightly more current to charge your battery slightly faster - all without any digital logic, protocols, or anything manufacturer specific.

Anything more complex with sense resistors, ID chips, extra wires, etc. just costs more, and provides less utility, and almost looks like a deliberate attempt to reduce compatibility and increase sales of chargers.

The resistor setup is both simpler, and unlike the memory chip, can't easily be repurposed for DRM.