> I can fully understand that they don't want to weaken that by supporting fundamentally insecure devices.

Except that there is nothing fundamentally insecure about them, they just don't support a specific convenience feature. You can straightforwardly support PIN-based unlocking by encrypting the PIN in ordinary persistent storage using a longer passphrase that only has to be entered during boot.

This is arguably even more secure because it allows the PIN to be dumped from active memory and require the longer passphrase again after a timeout, a limited number of bad attempts or in response to a panic button on the lock screen. Then the device doesn't contain the long passphrase whatsoever, instead of having it permanently stored inside of an opaque enclave that itself could (and often does!) have its own vulnerabilities.