I get the point, but can Stansted really be considered as being in London?
It sounds like a trick by Ryanair to make the airport sound more important than it is, similar to their airport Frankfurt-Hahn which arguably isn't anywhere near Frankfurt.
It's in Essex, and the London moniker is silly but it's a 45min train ride to Liverpool St so about the same journey time as coming from Finchley in London zone 4 (even if it does cost 4x more each way).
OK, true but for City that's a really small part of London: the Totenham Hale train station and its immediate vicinity. It's 46 minutes from Totenham Hale to LCY and 34 to STN. Anything further into London will win for LCY.
We recently flew to Gatwick and I was pleasantly surpised how quick everything was. Barely any waiting times, the hardest part was figuring out which train to London needs what ticket.
It sounds like a trick by Ryanair to make the airport sound more important than it is, similar to their airport Frankfurt-Hahn which arguably isn't anywhere near Frankfurt.