Here's what Steve Winter, who was part of the development team for 2nd edition, said about this--
This is a significant quirk of 2nd Edition.
Zeb hated the idea of secret doors being found with dice rolls. The only reason we kept the thing about elves and dwarves was because it was a legacy of 1st edition. This is hinted at (in a toned-down way, I assure you) in the DMG passage about elves and no one understanding how they notice concealed doors without looking.
Aside from elves, there is no check to find a secret door. You simply point to a wall and you automatically search 20' of it in 10 minutes.
This is closest to correct, only it's not even meant to be automatic. Players are expected to tell the DM what they're doing. Like the DMG states, "characters tap, thump, twist, and poke" until they hit the right combination. Further down the page, it states clearly that "It is a good idea to note how each particular secret door works and how it is concealed." That's the rule. To find a secret door, players must literally find it.
This goes back to the earlier discussion of narrative. We placed a heavy emphasis on it. Creative narrative always was meant to carry more weight than any dice roll.
This didn't sit well with everybody, as evidenced by the Int check described in the DL product. That's a kludge tacked on by someone who didn't like the tap/thump/twist/poke approach. It's not the 'standard' rule.