Noise is not the issue.
Typically, PS schematics show DC+ and DC- output. So my assumption is that with a linear unregulated PS, the DC is split into half positive and half negative? i.e. with a 72V output, is it +36 and -36?
If that is correct, then it seems logical to me that connecting the -36VDC to the chassis ground may have some negative effect. Yet this is apparently doable, so I have to assume there is something about this that I don't understand.
I am going to purchase a 12VDC regulated module specifically for toroidal linear PS that has a jumper for common ground with the HV, so the problem is resolved, but I still would like to understand it.