There are zero ways to use this cord correctly. Do not tell people otherwise. The proper generator connection is to, as you just said, use a proper generator inlet and interlock like you said you use. Anyone using a cord like this is using it incorrectly as there is no correct way to use it. Both the CEC and the NEC expressly forbid these. All it takes is for a child to unplug the wrong end and touch the exposed prongs and they will get shocked.
A proper generator inlet should have the male ends in a recessed inlet box connected to either a transfer switch or an interlocked generator panel.














I almost hit some 10 year old girl the other day when she wizzed out of 7-11 onto the road without even looking while on her e-scooter while holding a sluppee.