If I understand correctly, I don't think this is a userspace-breaking bug, as in: a kernel API changed and made a userspace program not work anymore.
It is a bug that prevents the kernel from booting. That's bad, but that's not the same thing. That's not a userspace compatibility issue such as the ones Linus chases. The user space isn't even involved if the kernel cannot boot. Or if it is actually a userspace program that causes a kernel crash, it is a crash, which is not really the same thing as an API change (one could argue, but that's a bit far-fetched, the intents are not the same, etc - I don't see Linus explode on somebody who introduced a crash the way he would explode on someone changing a userspace API).
It is a bug that prevents the kernel from booting. That's bad, but that's not the same thing. That's not a userspace compatibility issue such as the ones Linus chases. The user space isn't even involved if the kernel cannot boot. Or if it is actually a userspace program that causes a kernel crash, it is a crash, which is not really the same thing as an API change (one could argue, but that's a bit far-fetched, the intents are not the same, etc - I don't see Linus explode on somebody who introduced a crash the way he would explode on someone changing a userspace API).