> What are they using to switch all that current? No heat sinks are visible, so either the switching is really efficient or the drive electronics will overheat.

My guess, pretty well verified by some similar pics in teh teardown by kens in a sibling comment, is that the "the main PCBA was located. There were fourteen screws and washers holding down the board, which was probably done to reduce vibration on the critical components."

is probably the mosfets attached to the backing panel for heat-sinking, rather than specifically for rigidity.

If you look at one of hte middle images[1] you can see what looks like imprints of thermal paste around each of the mounting holes.

[1] https://daks2k3a4ib2z.cloudfront.net/5654e7207deb65b23ea76b7...