I'm wondering how many other private keys might be cropped to 32, 64 or 128 bit and much weaker than we think. Seems like nobody tested it yet. Otherwise the 8 bit would've been found within minutes.
If you've got the compute power, it's easy enough to have a go at it!
It’d be absurd to believe nobody tested these, and that no individuals involved in relevant standards bodies were aware of this weakness.