They should probably put the title as Medieval Europeans, the misconception that Medieval "people"/Europeans don't bathe isn't a global notion because Medieval people from other places bathed such as the Japanese.
E.g. while one might write about "Medieval China", the actual periods of history of China is better described in terms of dynasties (Han, Ming, etc.) -- and of course it doesn't come with the same connotations the term "medieval", "dark ages" comes from in Europe, nor there is a subsequent "renaissance" or "age of reason", etc with the same connotations as Europe (there is a period often referenced as renaissance, but it's about a new "golden age", prosperity etc.)