Every Qantas economy seat I have had has a rail around the front of the space underneath to prevent things stored under it moving forward or things in front of it moving under it. This indicates to me that the seats are designed to have things put under them from the rear.
It also just makes sense that when you choose to store a bag on the floor, you do so in your own leg room. Don't like you legroom being taken by a bag? Store it overhead. If you store a bag under your seat, in the person behind you's legroom, they have no choice in the matter.
It also just makes sense that when you choose to store a bag on the floor, you do so in your own leg room. Don't like you legroom being taken by a bag? Store it overhead. If you store a bag under your seat, in the person behind you's legroom, they have no choice in the matter.