Heavy filtration sort of gets mixed in with heavy flow in the tank (as filters are typically the main providers of it).
Heavy flow in planted tanks is primarily warranted when injecting CO2 and adding ferts as it helps to better ensure equal dispersal of both of these throughout the tank. Dead spots are typically unwanted.
Without CO2 and ferts, heavy flow is not as necessary (other than that required to effectively filter the water - but water filters provide for more than enough of that). In fact heavily planted (Walstad type) tanks can get away with no flow (and no external filtration as well).