Well, yes, they appear to be suggesting that Tottenham Hale is London, but a bit of text on a website does not, in any way, mean that it is London.
They cannot overrule the NCoC or the Routeing Guide in that way. So I am not suggesting that their daft wording invalidates any tickets, however someone who does not know about the NCoC and the RG may think that Tottenham Hale is London and therefore may think that tickets are not valid that way.
It's rather like the Groupsave issue in another thread. A TOC may say on a website that they do not accept them, but unless the NCoC is adhered to and a restriction is printed on the ticket, then they can say what they like but they cannot break the NCoC and refuse to honour them.