The context here was "people who are having a hard time working in the US tech industry/being funded by US VCs due to accents". Obviously if you intend to work in the UK or another country which uses a different accent, it makes sense to learn in that accent. IIRC the phone bank people in Asia actually train people in specific accents based on the client for this very reason.

(A totally fluent UK/IE/etc English speaker probably is fine in any context, but I don't think someone learning from a webapp is starting from that point. If you are going to be a moderate speaker, it is better to be moderate in the target accent.)