I don't think so. As long as the diode is wired into the host according to grounding, it shouldn't be a problem if there's conduction between diode/module/heatsink.
Example: if diode is case positive, and you wire the driver/host as positive ground, then if there is conduction between diode and module/heatsink it would be fine. If there is no conduction, it would still be fine.
As far as I know, this is only a problem when you have a case polarized diode that is the opposite of the host polarization. If they are opposite, you would have to isolate the diode. This can be avoided if you wire the host/driver for the same polarity as the diode.