What is also annoying is the inconsistency between Sky channels. I'm not sure if this is due to a mistake in VM's EPG data, or Sky's actual EPG data.
I'm afraid I can't compare the VM EPG data with the online data from Sky's own EPG as they (Sky) have discontinued their online TV guide. (see <Here>
An episode of a program can be broadcast at the same time on two different channels and one of the channels allows you to watch without entering a watershed pin, however the other channel won't allow you to access the program without the pin.
For example Stargate SG-1 airing at 10am weekdays on Sky Showcase and Sky Max. You don't need the watershed pin if watching on Sky Showcase.
PG shows in the synopsis for that show on Sky Max, hence the need for the PIN, however it isn't classified on Sky Showcase so no PIN required.