Using parallel pins of a connector or parallel wires in a cable to increase the current capability is standard practice. It has been done for a very long time, probably since the start of electrical wiring.
It's often done so that a multiway connector can use smaller pin/wire thicknesses suitable for the majority of the wires and just use a few pins/wires in parallel for the high-current power/ground connections. That happens in cars, for example.
Another is to allow the different current requirements of different power connections to be met by using different numbers of parallel pins/wires for each. That happens on a PC motherboard power connection, for example.
It is usually important and favoured to ensure that the low/zero voltage return path gets given as high or higher current capability than the power supply paths.
This is to ensure that high supplied current cannot cause excessive voltage drops in the return path, causing excessively different ground/0V voltages at connected items that require a common ground/0V. They'll be slightly different anyway but normally tolerably so.
Some systems perform a hot connection: a connection/disconnection while the connector wires are active. Some don't, only doing so when power is off. For the former, care needs to be taken about how pins gradually meet as only one connection of many may momentarily be made. But that's part of hot swap design which is a subject in itself.