Well...
Historically, in the cases of both England and Sweden, the state religion was changed by the ruler while the whole country was still practicing catholicism, and then the change went on from there.
So if the AI would sometimes change state religion as a first move to reform the whole country, then we might get more historical results for such nations. Or maybe it already occasionally does that but I haven't noticed? There is also the question of course whether this is really desirable for all countries from a performance perspective.