I figured out years ago that my own body temp is down in the low 97s. I would feel feverish but couldn’t “prove” it because I was reading 98.6 or 98.5. Later, taking my kids’ temps when they were not sick, I realized their normal temperatures were lower as well. Now, it turns out it’s not just us. It’s pretty much everyone.
Just another example of how a firmly established fact can be slightly wrong … wrong enough to cause us trouble.