Excellent question
You are correct you do feed less the Dubai Mall case study showed this with a reduction in food bill per month from $10,000/month to $4,000/month
The food has no effects on PO4 the product is not fortified with ash found in the many of other foods, it also contains a Ferrous sulphate monohydrate (a PO4 binder.)
Ferrous sulphate monohydrate is a mineral additive. As a blood tonic substance to livestock, it can stimulate the growth of animal's body. source of iron, promotes oxygen-rich blood, immune support.
When the likes of Dubai Mall are throwing in over 20Kg a day, a food with a PO4 source would be very detrimental.