Interesting results. Particularly they barely found a speed-up of newer compared to older LuaJIT versions (rather the contrary). Maybe they should have used the Are-we-fast-yet suite instead of the (random looking) set of microbenchmarks. I did measurements of Lua and LuaJIT some time ago based on Are-we-fast-yet and saw significant differences in LuaJIT performance (see http://software.rochus-keller.ch/are-we-fast-yet_LuaJIT_2017...).

I also compared different PUC Lua versions in an earlier measurement (see http://software.rochus-keller.ch/are-we-fast-yet_lua_results...) and found similar significant differences between versions.