There's nothing in that provision that even hints that the delivery of a service or good in an open market transaction and at a market price can constitute a gift - especially, as in the case of rents in RPZs, the quantum market price is constrained by law.
Read sub(2) again
(2) A person is deemed to take a gift in each relevant period during the whole or part of which that person is allowed to have the use, occupation or enjoyment of any property (to which property that person is not beneficially entitled in possession) otherwise than for full consideration in money or money's worth.
ie. a person takes a gift if they are allowed to have use of a property otherwise than for full consideration ie. full value.
If you grant an RPZ capped lease to a tenant, you are allowing the tenant to have full use of the property otherwise than for full consideration.
The landlord's motivation in doing so is irrelevant.
See also sub(3)
(3) A gift referred to in subsection (2) is deemed to consist of a sum equal to the difference between the amount of any consideration in money or money’s worth, given by the person referred to in subsection (2) for such use, occupation or enjoyment, and the best price obtainable in the
open market for such use, occupation or enjoyment.
It is the open market not the government imposed market.
These are also deeming provisions ie. a provision stating how something is to be treated even if what is actually happening in real life is different.
Again, before I'm accused of scaremongering or worse, due to policy considerations, I can't see this approach being taken by Revenue, so we are discussing an academic issue.