The presumption is that the contents being secured are /so/ valuable that locking my device is preferable to any leak of them whatsoever.

This is military level security and just isn't appropriate for most consumers. Particularly around something so rarely exercised and utilized by users as the boot process. A simple warning with a long timeout would have sufficed.

Aside from that you have a hardware vendor, sourced into an integrated product from another vendor, sold to a user, with various third party software interacting with it. This was always going to result in questionable experiences for end users.