Looks like a major score!
The ones I have here (I was bagging them for Goodwill) come right off the cotton fabrics.
Soaking would loosen it but also might create a mess.
Is the paper covering the entire back of each sample?
Because, if not, if it were me, I'd just hack it off.
You didn't pay anything for the material, and wasting hours trying to soak it off for another inch or two of useable fabric hardly seems worth it.
There's certainly enough there for a couple of quilts, if not more.
Have fun playing and designing with all the different pieces instead, if possible.