are there, among the various hadrosaurian remains ,unetched bones?
No. All four caudals and the dentary fragment have surface damage.
what about the predator's ones?
"None of the bones exhibit any surface modification such as weathering or abrasion-induced damage. Except for breakage resulting from recent exposure, elements appear complete."
So yes, I agree that an acidic environment cannot be the reason for the etching.