Hmmm, the only thing I can think of that he may have meant is that you have firm, dense skin that the needle would not push into easily? I'm not sure, but this would be my guess.

As a Massage Therapist / Student,I have found people to have all sorts of skin textures. Some people have very thin, translucent skin, while others may have thicker, more dense skin like I mentioned above.

I'm not sure if this is what the tech meant or not, but in my opinion that is what I would guess. Hope this helps somewhat!

Best Wishes,
Zen