Nice review. One issue with the Kuat and most others is for bikes that have fenders.
That's why, for example, the Hollywood Sportrider SE2 has an advantage in that it secures the bikes by their frame (top crossbar). Some bikes with non-horizontal crossbars, of course, may not work well, and some bike owners are very fussy about anything touching their frame.
With a single eBike on the Hollywood rack, I only saw about a 10Wh/mi hit on two 500 mile drives. Your setup with two bikes has a lot more places to increase drag, so it's not surprising you're getting a bigger hit on consumption.
You mentioned on your video that with the two-additional bike extension on the Kuat, those third and fourth bikes can only be 40lb each.
Here's the issue: Rack is 50lb, let's call all four of your four bikes 40lb each. 210lb.
Even two 60lb e-bikes with the Kuat for a total of 170lb would exceed the vertical load limit of 160lb the Tesla MY hitch.
I would not expect third party racks to have any higher limit than Tesla's OEM hitch.