Boost rear hub spacing, why 148mm? Why didn’t they just go the extra 2mm to the existing 150mm hub spacing which is used on a lot of DH bikes?

Also while they were at it ‘the industry’ could have introduced 83mm bb widths for non-DH bikes too. Then they could make frames with decent mud/tyre clearance for a ‘normal’ modern tyre width.

Am I missing something/gone nuts/making some sense?

Again?

Not intentionally, have you got link.

2016 Axle Standards, Part 1: Rear 148mm Thru Axle Coming Fast & It’s About More Than Just Better Wheels

FWIW, you can buy a 83/150 B+ frame from Pact Bikes if that takes your fancy