The thought was that the higher your intelligence, the higher the chance you know what you're seeing. So if you have a high intelligence of say 19, then you need to design the check such that it's very likely you'll "succeed" in recognizing it, so with a D20 that means rolling under 19 (a 90% chance). A lower intelligence would actually be a good thing in this case, someone with an intelligence of 2 only has a 5% chance of "succeeding" and rolling under a 2.

Probably the confusing part here is that you still want to roll high, but it's strange that a high roll, in some way, isn't a success; you don't successfully recognize what you're looking at and that's a good thing. Even writing this comment I kept getting it mixed up, but I think mechanically it fits the theme well.