It would probably be instructive to know how actual charitable donations are handled in Japan.
I have no idea, but in a highly reciprocal culture I could well imagine that effectively punishing reciprocation in that way would be a political non-starter.
I definitely found it strange Japan is allowing the local governments to gift 50% back.
In the US, legally any portion of a charitable contribution you get back in personal benefit (e.g. an expensive banquet) is not tax deductible.