Surely the Buddha never said to do this as there is not a single case I have ever heard of where a dead being was able to eat food and drink from our dimension of living.
Tirokudda Kanda (as well as dharmafarer.org's traslation of Tirokuḍḍa Sutta) mentions doing this for the benefit of the dead. Meritorious acts cause positive telepathic vibes which can help betterment of the dead especially if the see and rejoice in the meritorious acts we do.
So this does not look out of place as a later composition. It is the merit that is given not the food.
Also even if you leave out food this can be of some enjoyment to the spirits. Say a person liked a certain type of food and you leave it out. His spirit would naturally be attracted to it through he cannot physically partake it. As I see this is not what is mentioned in the Sutta, but the transfer of merit.
Transfer of merit works in two way:
- Positive vibe associated with the positive through having a positive externality on the person concerned
- The entity rejoicing at good action creating positive karma and betterment on its own