This works on the same basis as the historical witch trial:
"Because it's hard to make someone admitted a crime, therefore it proves that s/he committed the crime?"
Doesn't make sense IRL, and doesn't make sense in a game either.
(Plus, your logic only works if
for the person who committed the crime will easily
admit that they did it... Yeeeeeeeah, that's complete BS)
(Plus Plus, this pretty much worked on the premise that its the PCs who will decide who's the criminal in the first place, as otherwise this makes no sense - Note that the skill at hand is "Intimidation"/social-based and not deduction-based)
(Even if not so, that just means the PCs can Intimidate every single NPCs
until they get someone with a different difficulty rating, of which no competent KP will even think of letting PCs do... The more one thinks about this the more problematic it seems...)