Non-Contact Infrared Thermometers (NCITs) are ideal way of quickly assessing whether someone as a fever or not, and does so with a reasonable degree of accuracy. Regardless of whether the device reads 100.1 or 100.4, it is still a good indication that they have a fever. The FDA helps to manage expectations with this https://www.fda.gov/medical-devices/general-hospital-devices-and-supplies/non-contact-infrared-thermometers
There are limitations to the technology, and that is not a reflection on the quality of this product. Infrared Thermometers are simply not as accurate as traditional thermometers. There are variables that can impact the readings, with the distance from the forehead playing a significant factor. They are designed to give a reasonably accurate reading, but the accuracy rating plays into the equation. The internal sensor component is rated of ± 0.2C° (±0.36F°), and it could be ±0.6C° when considering distance and other environmental variables.