Environment is everything for fungal diseases of plants, so there are other additional factors that can also come into play. For example the levels of nitrogen and potassium (and possibly other nutrients), the type of irrigation and the time of day it is applied, how far apart the plants are spaced, location in the garden and so on.
@Maryl, I heard back and it is confirmed that Alcea as a host is an error and it will be fixed. Lucky that you spotted and mentioned it!