Interesting, I didn't know that.
Realistically though, if you know what your typical body temperature is (mine hovers around 97.6 degrees), anything above 99 would be extremely alarming to me. So if someone enters their security gates and reads 100.3 degrees, they are free to walk in? Guess it can't be perfect at the moment.
It is not likely to ever be perfect. 1 Asymptomatic.
2, more specifically to the temperature reading point even if everyone got a fever, body temperatures of some commonly run high, or on the flip side, run low. Sometimes people with a low body temp see their temperature is 98 or 99 and they have a fever and are sick as as dog. It is mostly a part of making sure people feel comfortable to come in and spend money, like random bag checks.