Maybe it's along the lines of what you were saying... I'm thinking maybe it's God confirming to him that he is actually gifted to walk in this capacity. I could speak prophetically right now, by the Spirit of God moving in me and giving me what to say, but that doesn't make me a prophet. Even if it happened every day, because the Spirit is doing it for a purpose I could still say that I'm not a prophet I was just available for God to use me in those instances. But when it comes down to something that seemingly has no purpose, that is something God has placed in you, not just when he needs you to speak something, but he actually made it a part of who you are. That type of guy, I think could walk away from ministry completely and he would still see stuff.
I believe my dominant gift is teaching. The teaching part of me comes out and manifests all the time, doesn't have to be ministry or even a subject I am passionate about, I can begin to break it down, analyze it and show it to somebody with demonstration in order for them to get a better understanding. Most of my life I didn't even recognize it as a gift, but looking back, I see where it's been there...