I wouldn't say that the technique is accurate at all. However, it is reliable, if the measuring instrument (you) is well "calibrated" (trained).
There are lots of good cooks which go by intuition. After years of cooking, they have gotten a very finely tuned sense of how to do things. Their brain does what is best at - it takes all information available to it (memories, heat perception, smell, sense of passing time, etc.), does some unconscious pattern recognition, and arrives at the decision "the grill is at the right temperature now", which turns out to be correct. This is how they get consistently good results almost every time.
Cooks who do not have that kind of experience can try finding other means to get consistently good results. Measuring the temperature with a thermometer is a good one, since it is usually the most important factor in baking and roasting. They replace the decision based on intuition with one based on a technical measurement.
Advice like the one you discovered is well-meant, but misleading. When an experienced cook tries to teach you how to do it "their way", they try to put in words whatever they think is going on in their head. They know they use their hand to check if the temperature is good enough, so they try to tell you how they came to the conclusion, e.g. "if you feel a burning feeling in the skin after 3 seconds, it's all right". There are two problems with that approach. First, as Stephie said, the connection between external stimulus (heat) and its interpretation by your CNS that turns it into a thought ("I have a burning feeling in the skin") is very individual. Second, it is not correct that the decision ("now is the time to put on the food") is made based on just that one stimulus. The cook cannot tell you how they made it, since it is an unconscious process. They are second guessing themselves.
So, if you are not yet an expert-with-great-intuition cook, then using this method will not result in consistently well baked food. At that stage, if you want that, you should be using a thermometer.
There is nevertheless a reason why you might want to use the method. If you want to turn into an expert cook with great intuition, the way to do it is by training your intuition through multiple repetitions. Your learning progress is determined by a combination of the number of repetitions, and the attention/concentration you use in each repetition. So, if you take some moments to pay attention to how the heat feels on your hand when roasting your food, you will become an expert sooner than if you ignore the feeling. Still, if the quality of the food is important to you, you should rely on the thermometer and not the feeling until you have trained your intuition a lot.