It's true that the distinction is a bit vague, the term JIT is overloaded to enough that it stopped being a useful technical term.
Compared to 'JVM JIT' or 'LuaJIT': there is no instrumentation to detect what is hot or not. The CPU frontend will crack x86 instructions into micro-ops, while looking for some patterns to merge certain instructions or uops into larger micro-ops. The micro-coded instructions (like many of the legacy instructions) are likely just lookups.
Most of this is my speculation, mind. Modern CPU frontends are still kind of a black magic box to me, but I think they are limited by relatively simple transformations by virtue of being on the critical execution path.
Not sure what the distinction is but that's where it is to my mind