Good Lord. I did it again. My nick name is Dan Dan because I sign my name twice. At least now I know why I do it. Thoughtfully responding, then urgent phone call, sign off, then have one more hurried thought and sign off again.

Anyway, I missed a point. The heat of the motor in a suction cooled motor compressor requires that the gas flow is predictable over it. A medium temperature compressor might have a motor that was sized for a predictable power factor, gas flow, and amperage duty that will not portray itself in a low temperature application with the same refrigerant. I think the danger with using a high pressure compressor for low temperature application would be motor overheating as a result of reduced cooling effect from the refrigerant flow.

Would love to hear from the others as to whether I am on or off track here.

This is a very good question, in my opinion.
One Dan.