You are welcome, Brym, and thank you for the additional comments and suggestions!  We work with Asus closely and I will pass your feedback to their website contact issue to them.
I will also pass your comments about the product links to our web team. We do have a partnership program and we list partner company’s products and services on our website. So far, most of the partners are companies whose products are for business use, and hopefully over time there will be more products from companies for IT hobbyists  and DIYers will join our program, and we will certainly keep your suggestion in mind and consider listing them.
In terms of making a cluster for the EdgeTPU, most of the industry users who need this type of ML performance power, are using the Coral Accelerator module for that purpose, which give them the flexibility to design any number of EdgeTPU on board and use the PCIe bus.  We also have one customer who developed a host board to support up to 12 Coral M.2 modules that provides 48 TOPS ML performance, to offer a cluster alike solution you mentioned.
Using USB is somewhat problematic, because the peculiar behavior on one of the pin traces on the EdgeTPU that require reliable signal, and using breakout board with an additional connector will mess up the signal to the chip pins in a USB3 configuration. In fact, due to this issue, most of the RPi CM4 users are having a hard time to get Coral Accelerator module to work with CM4, as CM4 typically requires a daughter board with an extra connector.
That being said, making a dual EdgeTPU USB module with the necessary mux chip on board to enable USB3 speed is possible, and we have been looking into this option. But given the flexibility provided by the Coral Accelerator chip to allow customers to design whatever the ML power they need on their own host boards, most of our customers are going that route for higher ML performance solutions, so offering a product from us isn’t a high priority at the moment. But I’ll pass your comments to our business team, as well as to some of our partners, as they could also make such a product for hobbyists.
Your adapter solution is very cool!  Glad to know you got it to work, and kudos to your innovative solution. I’ll share it with our engineering team.
Thanks again for your interests in Coral and valuable feedbacks!
Bill