Hard to imagine unrecoverable device. Maybe physically melting it into the brick will do the job. In any other case it is recoverable: you can replace whole memory with a bootloader, other corrupted modules and recover device.

It's also not literally a brick, regardless of future functionality. The ability to metaphorically compare it to a brick doesn't seem to hinge critically on whether the metaphorical brick is a permanent metaphorical brick or a temporary metaphorical brick.

we have a saying for that, soft brick.

That wording manages to avoid answering the question entirely. It just shifted the ambiguity from defining the word “brick” to defining the word “recoverable”. Recoverable by your grandmother with dementia, before the next Matlock episode airs? Recoverable by one person on Earth for whom unbricking this one thing is their special interest? Recoverable by a hypothetical future technotopian society that we predict will be capable of vaporizing atoms and rearranging them into any desired form? Do you draw a hard line in the sand for everyone to share one definition? Or is it entirely subjective, a tautology, a self-fulfilling prophecy - meaning anyone’s feeling of brickiness and recoverability is valid by definition?