So I roll up on your frequency tracking 20 degrees left of the XYZ waypoint you want to direct me through, and pitch in with "London G-ABCD FLxxx heading 160". You acknowledge briefly, and 30 seconds later I turn right 20 degrees. "G-ABCD I thought you were on a heading!?" you protest. "No G-ABCD was instructed direct XYZ -- just took a minute to ident it"
Whether or not you use the word "radar" as the discriminator, doesn't it make sense to distinguish between "the heading I have been assigned" and "the heading I happen to be on" in the phraseology?