It won't function without a kernel, but will it not function without the Linux kernel? Since the Solaris days with lxrun all the way through present time with Windows 10's linux subsystem and SmartOS's lx-branded zones, you could run Linux binaries (and entire distros) on a system without the Linux kernel, with various amounts of support/breakage. Still, no GPL2 kernel needed.

I suspect that when a lawyer uses "essential and inseparable" they do not mean the same thing a technologist would mean. The GPL itself doesn't use that language, and anyway it's trivial to argue that a full OS distro isn't "based on" (the language of the GPL) the kernel itself.