Maybe he's using an older KDE release or on a not-first-class distro which doesn't ship with it out of the box, like Mint.
And correct me if I’m wrong but isn’t KDE neon supposed to be a bit less stable?
I haven’t seen it in a while, though, so it just might be they have fixed it. Fedora + zawertun COPR, for what it’s worth.
Trying to explain it I'm actually not sure I 100% understand the solution. It looks like it uses systemd for sleep AND saves all of the VRAM (I'm guessing into RAM if I'm using anything other than hibernate).