Well, not every vendor does it differently, because there are far more vendors than possible wiring permutations on a 3-contact connector... but I understand what you mean.

The same issue applies to PCB header pins.

And the same goes for 25-pin D-sub connectors, which have been widely used as RS-232, parallel printer, and SCSI ports.

Voltages vary, too.

This is why we check before wiring them to other things.