Very interesting Steve. I was minded to make a similar comment on the validity of the battery test.
A family member had a JLR vehicle from new, and when it was 3 months out of warranty, the stop/start stopped working!
Two battery tests with sophisticated testing equipment showed the battery to be serviceable. The vehicle then went to a well respected local JLR independent who tested it on JLR diagnostics, and it failed the cold cranking current parameter - even though the car always started without issue.
Rather sceptically, we renewed the battery with the equivalent Varta, and hey presto, all was well again.
Kind regards,
Gareth.