Most entries in the bestiary use the same graphics as display in the world, so resource packs will work as expected. However some bestiary entries use a separate graphic - the three you mentioned plus EoW are some I know of - so a resource pack needs an additional image to update the bestiary too. This is because the entry, in its normal form, would not be suitable for display in the bestiary. Using Skeletron Prime as an example from your screenshot, its hands would not normally be grouped together so close to its head.