While it is stated in the overrides themselves, we know that people don't always read everything they are supposed to. I think that a small section that explains that if they are using _WEBSITE overrides, they need to specify a website in order for them to work would be grand.
And hey, it'd help battle the green faster if we could just point them to the right area of the FAQ ;)
If it's agreed that this is needed, I could likely come up with some text for it.