Could be the article is written by someone outside the US. If you aren't in the US (I gather—at least in the UK I can speak to personally), the app just doesn't

Could be the article is written by someone outside the US. If you aren't in the US (I gather—at least in the UK I can speak to personally), the app just doesn't offer body temperature at all because they haven't bothered to get it certified for medical use. (You can work around this by spoofing your location, but it's not obvious to do.)