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.