Reno:
You mentioned...."The irony is that the fixture that started this thread would never be questioned by an inspector, no matter what horrors lay behind the backplate."
If said fixture was flush against the structure surface, NO, I would not be aware of any issue, as we (I) don't remove fixtures upon inspections.
When a luminaire looks 'odd' then I may ask that it be taken off/down for inspection. Your page 1 fixture would not get my attention, unless it was not 'flush'.
As to your shop made energy efficient luminaire, I would not have an issue with it, as long as there was plug connected. I will venture a guess that the cost between the page 1 item, and the 'shop made' is either close, or the shop made cost more. BTW..."nice".
