I declare that IMGUI performance is pretty gosh darn good! Some readers might have predicted IMGUI to be significantly worse as RMGUI. Instead we see numbers that are in the same ballpark.
Maybe, this is true, but it's not a conclusion we can draw from these tests. In choosing programs to benchmark, he selected notorious behemoths to pit against the IMGUI set—which, it should be noted contains stuff like Dear ImGui and EGUI, which aren't even apps.
And later, in the Windows benchmarks, he shows that the two apps—the only apps—in the IMGUI set actually perform worse than the others. The fact that RAD Debugger has a heavier power draw than clunky Electron apps of all thinks like VSCode should be considered evidence conclusive in the other direction.