I think container escape is well understood by most to mean (for Linux) cgroups and/or the stack most folks use (containerd, Docker). It's a generic term but useful term, like VM escape, even though there are many kinds of virtual machine managers and hypervisors.
the other reply alluded to this, but to make it explicit: nothing about this CVE requires docker and it looks like you should be able to do it with a few syscalls in any process starting with a call to unshare(), unless something else (like selinux) is getting in your way.