Having just looked at that linked page, it is very confusing. Although the map clearly shows all Greater Anglia services within zones 1-6, the page also lists Liverpool Street to Stratford as additional validity. That’s because it’s an interavailable route with the Central line so can be used after 0900 rather than 0930. I’ve a feeling that it’s a throwback from when the 60+ could be used all day (before my time of being eligible, so I might be wrong). I think TfL ought to consider rewriting that page a bit.