This isn't really a fair argument. As far as I understand, at least in the case of the 2006 plot, the bomb still needed to be constructed (i.e., ingredients mix

This isn't really a fair argument. As far as I understand, at least in the case of the 2006 plot, the bomb still needed to be constructed (i.e., ingredients mixed, detonator placed inside, etc). If you have something in a water bottle you're just carrying through security and it's volatile enough to simply throw at a crowd and cause harm, I don't think you've got a great chance of even making it very far, maybe not even to the airport in the first place lol.