This study is about air quality in neighborhoods. So it would show the same thing even if EVs just moved pollution from where people use their cars to where power plants get placed, because that's not the question it's addressing.
Even if the pollution is identical, moving it from where everyone lives and works over to more isolated areas where power plants are would still be a big benefit.
We know EVs are cleaner than that. And when the pollution is centralized in one power plant it’s also more economically feasible to apply filtration or particle capture isn’t it?
On the other hand you can't do that with combustion vehicles, trying to legislate more environmental regulations to existing cars is political suicide.
Nitrogen pollution is usually reasonably local to the plant but also can be srubbed. Its not practical to scrub moving objects, but it is for stationary generators.
Same with particulates, you can capture quite a lot with electrostatic scrubbers.