For anyone who wants to see what I'm talking about, here (https://www.youtube.com/watch?v=mBssIIRGkOw) is a good video of a 1970s minicomputer (which is not a mainframe, yes, but generally built and maintained by the same vendors with the same repair strategies) being disassembled/reassembled. You can see plenty of bodge wires!

You can also see the 1970s evolution of the "breadboard blackplane" into "pseudo-ball-grid-array backplane, with arbitrary collections of bodge wires loosely mated to it via hand-crimped proto-Molex connectors." (The only difference in practice being that you could now plug/unplug a "group" of wires, rather than one at a time. There was still no screen-printed indication of where on the BGA grid to re-attach anything, since the grid wasn't customized to its purpose, but rather was still fundamentally a "generic routing board" in the same vein as a breadboard.)