Reno:
Looking at your mock-up & the fixture IMHO the widget I have above would probably require some creative engineering to make an acceptable install.
I looked at your fixture, and I would have to say, I agree with your opinion that 'something ain't right'. Just for my own mind, was/is there any instructions to install it?
Also, I see what appears to be a 'tab' on the bottom of the fixture, which may indicate some type of 'back box'? But, with KOs for mounting to a box, as you have said, don't make any sense.
Wonder if it's a 'good' UL label?