Wow, that's crazy. I remember reading some of that back then. If I followed correctly, though, the burned out pump was a comment from a subsequent tech that never actually saw the pump in question?
My money is still on a stubborn air pocket, AHC-fluid-gel (there were contaminated fluid batches around 2020-2021, acknowledged internally by Toyota in Nov 2021, supposedly) or un-primed pump. The final pump install probably just went more smoothly or a tech properly primed the pump. That wouldn't be the first time that dealers were completely perplexed by a failure to pressurize and/or a pump assembly replacement for a non-pump problem. If the pump got gelled by bad fluid that could gum up the first pump AND the subsequent replacement. The pumps are fixable - just have to disassemble the pumps and clear out the mesh screens - but I'm sure that's beyond their scope of work. Just throw another $5k assembly at the problem, haha. By the time they added the final pump, perhaps all the gel had been sucked into the previous two pumps and was out of the reservoir.
Side note, I'd love to see how Mercedes does with their far more advanced hydraulic systems. They're German - so you'd assume more complicated for a similar level of performance - and also way more involved than the Lexus//Toyota system. Toyota/Lexus AHC is ~750 psi. Mercedes is 3000+ psi with no mechanical spring to assist.
