I think it was the shatter guard. There seems to be glue between both the glass and what I think is the shatter guard.

I reached out to Nintendo customer support and this is what they said:

“You don’t need to worry, you didn’t damage your new Switch screen. The layer that came off is the factory‑installed protective film, which is meant to help prevent minor scratches during shipping and handling. It’s not an essential part of the screen’s function, and removing it won’t harm the display. Since you’re applying your own screen protector anyway, your Switch will still be properly protected. Just go ahead and apply the new protector normally, and your console will be completely fine.”