There seems to be a couple of fundamental misunderstandings here in the article.
First obvious one. Body temperature is CORE body temperature. Skin temperature is always going to be lower. 91-94 is probably average if your body temperature is is also average though it's extremely variable because of ambient tempand evaporative cooling.
The thermostat inside a kettle, and the ember mugs, are also woefully inaccurate. I just checked mine against a Fluke 54-2 and Klein IR thermometer. My Stagg EKG Kettle was 7 degrees off until around 160 degrees F where they are calibrated towards, and it was closer. The Ember mug set at the same 134 degrees was 121 with the Pixel reporting 117.
The Pixel uses an IR thermometer. It's extremely sensitive to angle and distance. I'd guess at the 2" distance it probably has a 2" target that it will average. Likely getting the edges of the mug into the averaging window skewing results. Also, holding the phone above a boiling liquid will quickly fog the IR lens and make the results irregular quickly explaining your 50-degree delta, zero chance you could keep the device within 2 inches of a boiling substance without it fogging.