J, back in the olden days nothing was really hurt if the motors were running the wrong way. Things just didn't work and at a certain point you might start running hot because the blowers were not moving enough air but usually you couldn't get it doing enough to warm up.
That was when one of the things running was the hydraulic pump that made things go. It got serious when disk drives stopped "unloading" the heads. If you spin up a drive backward the heads will not "fly".
They put in a phase rotation detector that interrupted the power on relay circuit so you just got a red light. You would pull a plug, swap it 180 degrees and plug it back in. That swapped 2 phases.
