This is true, but it can't apply to the kernel. If your kernel has crashed, it is a terrible idea to try to write anything at all (such as a screenshot) to the

This is true, but it can't apply to the kernel. If your kernel has crashed, it is a terrible idea to try to write anything at all (such as a screenshot) to the disk -- because the kernel's safety guarantees disappear in such a situation, you're likely to make a bad situation worse and e.g. corrupt the filesystem.