Because from their perspective, things don't look like that. From their point of view, it probably goes something like this: "The worker is supposed to work extra hard, but now they are resting, AGAIN! Now I'm gonna say something so they finally start working again" without considering any other perspective about situations.
It's really hard to read people without speaking to them, and most middle-managers just try to read people even though most people are honestly pretty shit at doing that, so they misread situations all the time.
In this particular scenario, notice it says "I'm thinking..." instead of "I said...". Not sure why they didn't tell their supervisor "I'm hot and about to faint", but knowing the average supervisor at Amazon, I do understand why you wouldn't talk about it.