Maybe the former Presidential-hopeful didn't realize he needed to upgrade to the Pro version of the app. Then his iPhone would not only measure temperature, it would also measure current PSI (PM2.5 included), tell you if you are having your period, and cook instant noodles.
Good thing he didn't try to measure boiling water.
In the comments which ensued, a commenter pointed out, "The phone is not a thermometer. The app merely gathers temp data from other sources."
Mr Tan replied, "You got the right answer. I realized it after a while. Haha."
Mr Tan went on to quip, "My $700 iPhone cannot measure temperature. A $3 thermometer can. What an irony." #fail"