Natural ventilation adjoining extra room

[Shepplexor]

I am working on a historic building retrofit into apartments with natural ventilation. (The windows open.) Some of the units have an "extra room," which has no windows and only a doorway to the main living space. The doorway is a standard 2.5 ft wide door, not nearly meeting the 25 ft^2 opening requirement for adjoining spaces. This would suggest mechanical ventilation is required in the extra room, but the ventilation requirement in Table 403.3 is based on the number of bedrooms in the whole living area, not an individual room. Plus, practically speaking, I've never actually seen an apartment with an extra room that actually does this. What is the intention of the code here? Obviously the contractor will not want to spend money on mechanical ventilation when they were relying on the windows to avoid that, and it will be a difficult discussion that common practice is wrong. I thought about putting transom windows above the doors, but I'm not sure there is enough space.