Reported by ardox14 in Curseforge comments:

There is some question. In Classic version, with autoloot enabled, when rightclicking on the mob corpse, and some item dropped, pop-up "Pick up this item will bind it to you" doesn't appear. But this item doest't picks up into my inventory (all others picks up). It requires to mouse click on item in loot window to pick up it.

Is it a bug? Or that's an API restriction? Can it be fixed?

it does, it just cost me Old Ironjaw when fishing :-( it removed the message that there is something BoP you need to confirm but the item was not looted - I missed that and fished again before I clicked on the item -> loosing the loot :-(

Recent changes to the loot module may have fixed this. It needs to be retested in Classic, but I don't have a toon that can do that.

Ideally need someone to confirm whether this is still occurring in Vanilla-Classic after the fork to TBC Classic.

Investigation suggests ConfirmLootSlot() requires a hardware event on Classic. There's no lua error, and the item loots correctly without confirmation if you click on it. Events are firing as expected, although strangely, LOOT_READY is firing after LOOT_CONFIRM_SLOT. Either way, I tested a sample chunk of code that waited for both events, and the results were the same. No lua errors, no indications of a problem, other than the item not being looted. I tested another, similar addon that uses a secure hook for the loot, and that showed the same behavior: it still required clicking the item in the loot slot.