HN user
Oh - I thought this was for using USB devices on the ADB Mac, not the other way around.
There are options for using modern USB devices on ADB as well, such as the ADBuino (https://github.com/akuker/adbuino) and my fork called HIDHopper (https://github.com/TechByAndroda/HIDHopper_ADB).
Yeah, I noticed that chip and didn't give it a second look. It's more than 3x the cost of the PSRAM solution, and that would have driven up the price of the RAM card higher than planned. So sure, it exists. And that's about all I have to say about it.
Hey cool, my RAM card is being mentioned on hacker news!
You're right, the card uses PSRAM because non-synchronous SRAM chips basically aren't available new any more. I didn't want to have to troll the depths of (semi-questionable) new old stock parts sites and went with new chips.
This design was assisted by my good friend techknight, original designer of the 8 megabyte RAM card for the mac portable.