I know some bay area inspectors are saying once CA starts using the 2023 NEC they are going to require all panels to have SPD's
215.18 states that feeders that supply dwelling units require SPD's. It doesn't say that all feeders supplying loads in dwelling units. To me if a feeder is supplying a dwelling it must meet the definition of a dwelling.
3 bedrooms and 2 bathrooms is not a dwelling unit.
A kitchen, family room, bathroom and foyer is not a dwelling unit.
A garage and laundry room is not a dwelling unit.