A Ford style starter relay is at least different from continuous duty in that a starter relay has a bigger, higher power (current) winding to pull the contacts in much harder. This results in higher current capacity for the contacts but also means, that a starter relay coil will burn up and cook if left powered too long.
It's possible a CD might use the same contacts and construction, but they use a ligher coil with less "pull" which willl not burn up. And, the contacts have less current capacity because of this
