Not necessarily, for example, the dealer is not required to even see your LTCF because it is not necessary to purchase a firearm. Thus, he can assume that everyone who purchases can legally carry it loaded in their vehicle.
You're right, I can't see a definition of a secure carrier. But making an effort to carry it securely and unloaded, even if not in a case, may be sufficient. I don't want to be the one to be the test case though, nor could I since I have my LTCF :)