“Strike me down in anger and I’ll always be with you, just like your father.”
It’s clear to me he meant that Kylo would be haunted by his evil actions (for which the new vision scene works great) not that he would literally come back as a spooky ghost to haunt him, even if that was a thing in DotF.
Luke doesn’t even let him strike him down, it was just a warning that the path he was holding to would just bring him more pain.