Feynman understood the difference between knowing the name of something and knowing the thing itself. In the first case, we know that something exists and have a way to name it. In the second case, we have enough of an understanding of the thing that we can describe it to others. In the best case, we can teach it.
An important detail about the technique is, that it is about learning, not about teaching. It is there to serve the one who applies it to learn.
If learning requires this type of engagement, the question becomes, what is your teaching for?
There are more than a handful of answers to this. It’s a matter of choice and worth it to drill a bit further down by asking yourself what your teaching will enable the other with. It gives a way to see if your teaching worked. And with a bit of luck, it will also help you to stay within the reality of what your own learning allows you to do.
Feynman knew that the first few times around what he would detect were his gaps in understanding. It took him a while until, for some of these gaps, he became able to pinpoint that they were not his and instead gaps in the existing understanding of physics.