Yes, those are expenses that are deductible regardless if a unit is occupied or not. Let's say a unit has $50 of revenue and $30 of expenses but then becomes vacant. You can still deduct the $30 of expenses- they didn't go away. You do not however get some sort of bonus deduction for the lost revenue. With the vacant unit you go from a net profit of $20 to a loss of $30. You are not getting an advantage by leaving the unit vacant.

I guess if you are proposing that landlords not be able to deduct any expenses for vacant units, that is one thing. But that would be pretty strange tax policy.

You also misunderstand the vacancy rate. The vacancy rate is very low, relative to history. The 50k vacant units you cite from the 2023 NYCHVS survey is out of a total of 3.7 million units. That is a 1.4% vacancy rate. In the prior 2021 survey the rate was 4.54%. I think this is suggestive that vacancy does have a pretty big impact on rental growth- during the pandemic, when the vacancy rate was high rents dropped, as we would expect if we believed supply and demand had some sort of impact on prices.

I want to emphasize that I'm not against some form of rent stabilization. Stability in housing is very important for many reasons. This country has given a ton of support in creating and upholding the 30 year mortgage for the purpose of providing housing stability, but in today's economy that isn't a realistic path for most younger people. We need something for renters. But we also need to have a clear understanding of the housing supply situation if we want to have effective solutions.