I think the body is almost always correct.
He may be on NSAIDS to keep the temp down somewhat; but even with those, I’ve had ‘flu and broken out in a big sweat anyway at night when it all broke. Didn’t need lots of covers - body did it by it’s own self.
When it hit my wife and I late in December 2019, she spent three weeks getting over the symptoms, which included fatigue, loss of taste, and loss of appetite. She had no energy, but she never had a noticeable fever the entire time.
OTOH, I woke up in the middle of the night in a huge sweat with no symptoms of being sick prior to going to sleep. It was like someone had dumped a large container of water on me. I was a little tired the next day, after which I had recovered with no other symptoms.