> The obvious one is that the security domains in the device are idiotic. There's a "secure" processor with almost no processing power or IO, and a "insecure" one which handles the screen, buttons and IO. Both of them handle secrets (for example, the seed shown on the screen), which leaves you with essentially no gain whatsoever.

I think the idea is that the secure processor will verify the insecure processor's firmware (the "MCU check"), making such attacks impractical.

Of course, the design is broken and it can be bypassed by emulation, but security isn't all or nothing - "no gain whatsoever" is not true.