There's
no "supposedly" that TT use
Golden Promise - they are famous for being one of its biggest proponents.
But the identification of Wyeast 1469 as their yeast is more problematic. For one thing the commercial homebrew yeasts are almost always single strains whereas most of the British regional breweries use a yeast that is at least two strains, typically one for flavour and one for performance (think Windsor + Nottingham) so this idea that a homebrew strain is equivalent is always going to be difficult. Plus strains mutate once they have been separated - there's been quite a bit of mutation among the commercial versions of Ringwood for instance. But in this case the identification looks particularly problematic as DNA analysis shows that 1469 seems to be a Wyeast version of WLP022 Essex. That also means that it doesn't fit the history, as the TT yeast supposedly came from John Smith via Oldham, and the Harvey's yeast which also came from John Smith are nothing like WLP022, the Harvey's isolate that's been sequenced is completely unrelated to 1469, in fact it's a POF+ member of the saison family. It's possible that the TT multistrain contains both a WLP022-like strain and a saison type, but an easier explanation is that something got mixed up somewhere along the way. Unfortunately there's not a lot of proper square yeasts that are readily commercially available, certainly not Stateside, so there's nothing wrong with 1469, but just don't think that it is necessarily "authentic" for a TT beer.
You may also enjoy this
tour report, and there's a
good video on Youtube.