I think it s a response to the "containers can't contain agents we need VMs" which didn't go far enough. Qemu/KVM is the type of software that maybe isn't fixable, it has a huge surface area of features (all in memory unsafe languages) that have to be fixed, and maybe its not going to be fixed. If everyone who needs strong security reads this and uses firecracker or whatever instead (I mean, they probably mostly are), then maybe there will be even less pressure to fix the convenient stuff in Debian.