I think you misread the graph. "Active Cooler in Case with HAT" is pretty much the same temperature (74.8) as "Active Cooler" (no case, no hat, 70.6). None of the configurations with the cooler throttled.
Ah shit, you're 100% right. Looking at it on my computer monitor I think I was looking at the "Heatsink in Case with HAT" line color by mistake. My error and apologies!