In what way is thermally throttling at 86.5 C quite enough cooling? "Active Cooler in Case with HAT" idles near the same temperature "Active Cooler" reaches under max, unthrottled, load.
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!