This is quite bizarre. Even more bizarre that they expected you to call them by it. That would weird me the F out. In short, I'm actually pretty surprised people share this information at all (aside from if the question is asked), let alone expecting others to use it. I kinda get
@A300Capt 's experience, when you see a guy or gal you previously flew with in the military, yeah I might call them by the callsign I know them by, in passing. But most of the people I know from the military don't work here, so there is a low probability of this happening.