That's pretty fascinating; I'd love to hear more about your various plant tours. Roughly when did you visit BMW and Tesla? Also comparing it to pre-2010 would be interesting. Thanks!
It's just been far too long for me to remember NUMMI that well, but as far as I remember, it was a pretty automated plant. At Tesla, I saw tons of forklifts being driven around manually, occasionally bumping into things, one with a broken piece of pallet stuck under a wheel, people hand-polishing parts, etc. Workers with boomboxes setup in their desk area on the factory floor, fun stuff like that. I don't begrudge them this, as they have tons of space and are building a car company from scratch; it won't be as automated on day or week or even decade 1 as an existing established manufacturer. But when you compare to BMW, where virtually every operation is highly automated, it's quite a change.
Of course, there's also the matter of what the manufacturer is willing to show you (perhaps we didn't visit the forklift floor at BMW!), and also BMW is highly space constrained building cars right in the heart of Munich.