There's a middle ground between Apple's rounded corner land grab and allowing non-compliant electrical devices that can cause property damage.
Consider the situation with standard NEMA 5-15R receptacles. As far as I'm aware, the design is not legally protected, but any manufacturer who made a '5-15R' receptacle that couldn't carry 15A--or any device manufacturer who decided to re-purpose the pins such that the ground conductor carried 240V--would have legal problems if they brought their product to market.
This is where USB-PD should be: in a situation where physical connector compatibility brings with it enough design assurances that any pairing of legally-available devices won't blow up, catch fire, or burn out. Ideally, any USB-PD device pairing should work, but at the moment the bare minimum needs to be that any device pairing is safe.
Consider the situation with standard NEMA 5-15R receptacles. As far as I'm aware, the design is not legally protected, but any manufacturer who made a '5-15R' receptacle that couldn't carry 15A--or any device manufacturer who decided to re-purpose the pins such that the ground conductor carried 240V--would have legal problems if they brought their product to market.
This is where USB-PD should be: in a situation where physical connector compatibility brings with it enough design assurances that any pairing of legally-available devices won't blow up, catch fire, or burn out. Ideally, any USB-PD device pairing should work, but at the moment the bare minimum needs to be that any device pairing is safe.