How does the first quote compare to the second quote. Who decide that the first represent an acceptable attempt while the second does not? How this this actually look like in play if a player states "I pick open the safe to find the Desert Rose ruby" and you think this is inappropriate, while the player thought it was justified? How do this compare to how play would be if someone was "picking a lock to get at the documents inside the safe"? (It clearly is not established in the fiction that there are documents in the safe, as "still there" is a success outcome for the check)
"Documents" is vague. Many entirely distinct things could all meet that description validly, e.g. receipts, letters, books, notes, pictures, all sorts of things.
"Documents" are fungible. Any
copy of a document qualifies, so there could be duplicates.
"Documents" can be found piecemeal, where you find some but not all of what you wanted here, and more of it elsewhere.
"Documents" are a lot more likely to be found in specific places and not others, as a general rule, so simply knowing that they're documents gives you information on likely locations, which I had left out of that example for simplicity's sake. A desk is a lot more likely to hold documents than a liquor cabinet.
None of this is true of a singular, named ruby that is (I hope you'll grant, as it wasn't
technically specified) specific, unique, singular (meaning, it's not "the Desert Rose
s", there's only one of them), and not particularly associated with any location or uses beyond "looking pretty", at least not anywhere near to the degree that "documents" would be.
Established fiction matters--and the fact that one has established the target as "the Desert Rose ruby", vs having established "the documents" as the target is part of that mattering. Different fiction, different expectations.