The power connections are not the problem. How the PSU's work is the problem: Modern miners do not use a fixed 12VDC input like older miners did.

In older miners 12VDC was fed to each hash board and each board had a second regulator on them that lowered the 12V to a level suitable to feed the strings of chips. Those secondary regulator introduced an efficiency loss. Modern miners directly control the PSU to set voltage to the strings and that voltage will be somewhere between 15 and 21VDC depending on the model of miner so now not only are there more chips in each string but the voltage fed to them is now directly adjustable by the miner controller.