Maxperson
Morkus from Orkus
Why don't you just ask to see their character sheets, so you can point out how obvious it is that one of them has a higher Int? "Look! This one has a 17 and this one has an 18!" Of course you can figure out who has a higher bonus by looking at the dice rolls, but that's irrelevant because we are talking about impact on game outcomes, and for that all that matters is pass or fail. Fact.
Tiered DCs are of course permissible, but a few posts ago you were dismissing pemerton's argument because his NPC's weren't RAW, so I shall do the same here. Likewise with your use of rules from previous editions: irrelevant.
So with this you're saying that it's impossible to make a Holmes or Holmes-like PC in 5e, because Holmes had tiered answers that were better than other detectives' successes. Without tiered DC's, a Holmes like character can't be made.