- Apple made some different standard that uses the same Plug
- Power supplies come at different power ratings (who would have thought!)
Of course this is not ideal, but it is already better than not being able to get _any_ 3rd part power supply at all.
Such device would be either quite "fun" to use, unless it had type C ports marked with dedicated functionality, so you'd have to be careful what device you plug to what port.
AFAIK there's no protocol to control other ports via PD from the port you'd connect to the "main" device (like your laptop). So the behavior would be all pretty random, or the ports would have to be fixed in function.