The best part of the new "defense against Spectre" is that the LFENCE instruction has been around for ~20 years. It's not even not a defense against all variants.
So what? The defense relies on it serializing the instruction stream which is not necessarily true based on the semantics of the instruction (until it was retroactively documented to do so)
lfence behavior varies. On AMD CPUs you need to set an MSR to make it serialize instruction dispatch.