It is also possible that it is currently intended like that by Larian, however inconsistent that makes the game be. Indeed, there's one time in the game where the character doing the conversation can drink a sleep potion, and if you do that, the character normally falls asleep. Haven't tried with an Elf, but maybe they have so far implemented the rule that drinking a sleep potion makes an Elf fall asleep just so that this sequence works (instead of writing an alternative sequence for an Elf character).
On a related note, Elves are supposed to not sleep at night, but meditate/trance instead. When you have a tadpole dream, you can protest that this doesn't make sense and you don't normally sleep, to which the dream replies that yes, but this dream is special, so that's fine. What's not fine is that when Astarion comes for a bite at night, your Elf PC will be sleeping like any other PC, and there is no acknowledgement of that.
I am hoping that, for both these cases, the writers will eventually write an alternative for Elves, and that the game will not resort to inconsistencies "because writing reasons".
On a different note, I have not experimented with potions as drink vs thrown. I'm very curious about buff potions. If I throw a Healing or Speed potion near my allies, do they get the buff ? Can this turn a single-person buff into an AOE ? I hope not.