I'm not an economist but this seems pretty dumb? To the extent that it helps someone afford a home that they can save tax-free for it, the same is true of some of the people they're bidding against, driving up the price they ultimately pay for it. The government is just transferring their own future tax revenue to people who own homes, not people in the market for them.
It seems that governments have a reflex of dealing with a supply crisis by showering money on the demand side (see also: gas tax decreases, higher education subsidies, etc.), which just drives up prices further.