That's a Routeing Group, that isn't the same as a station group.
I still agree that it makes sense that you can't start your journey by walking to a different station to that/those named on the ticket that is on a completely different line. However I can't find anything that actually says that, so I can see why HHF think it should be valid.
I still agree that it makes sense that you can't start your journey by walking to a different station to that/those named on the ticket that is on a completely different line. However I can't find anything that actually says that, so I can see why HHF think it should be valid.