Thanks for the explanation.
Just to add to my confusion: the Fare Finder from Streatham to Putney Rail (5 minutes walk from East Putney Tube) *doesn’t* default to Zone 1- I presume it’s based on Streatham – Wimbledon – Clapham Junction – Putney which is fine, but then why doesn’t it default to via Wimbledon to get to East Putney too?
The TFL/Oyster default fare calculations seem very opaque.