Well, if you didn't go crazy sanding it off, you probably still have some of the original finish now acting as a sealer, so that could explain things. Personally, if I felt I actually got down to bare raw wood, I'd not feel comfortable without at least doing some kind of sealing process, like gunstock oil, or something.
I also had the shop do my older NYC, and they definitely treated it with something... I think they used the gunstock oil, but not sure. But it feels absolutely beautiful. I'm strongly considering doing it (probably myself) to my newer custom NYC. It is a pretty straightforward process, so if you're careful, it works just fine.