I think this is less and less true. Cars are very well tested now, and they rarely design something 100% new. By now the build processes are well know, and we are just talking about subtle refinements, even with a new model like the Defender. I am certain a lot of components are derived from existing models. We bought a first year (2016) F32 BMW 340i M-Sport and have zero issues so far (44000 miles).
I agree, the testing JLR do on components in the factory and real world seems to be very good these days, JD power seems to back that up, they are improving, but issues are mainly infotainment related, imo with Android Auto and Apple carplay + SOTA & FOTA, future issues will continue to drop.
Cars will become like phones, when manufactures are aware of a software related issue they issue an update, which you activate at home on wifi or with the cars wifi hotspot.
They will also drop new features that improve experience to keep customers happy.
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