Yet another reason why developers don't want to provide affordable housing
There was no allegation that the apartment complex was not meeting its obligation, only that there were some vacancies.
While the court went through some understandable gyrations given the language of the statute, agreement and relevant principles, ultimately the court relied on the doctrine of "strict application" of tax exemptions rather than on the requirement that interpretations follow legislative intent. The extreme result is that instead of the non-profit owner of these units being exempt for taxes on 75% of the units, the owner is subject to property tax liability for any units not so rented.
You can see the result coming: landlords won't sign leases for affordable units that don't provide a requirement for occupancy on January 1. Then the appraisers' will attack that and demand some "proof" that someone was actually there. It's just foolish, and this decision, while intellectually consistent, simply creates absurd results that would not have been contemplated by the Legislature.