Each of the seventy-two three-letter groups is completed with one of two endings. Some take -el, from El, God. Others take -yah, from the first syllable of the Tetragrammaton.
Both elements are entirely ordinary in Hebrew naming and long predate this system. Michael, Gabriel, Raphael, Uriel and Daniel all carry -el; Isaiah, Jeremiah, Obadiah, Zechariah and Elijah all carry -yah. Angelic and human names share the pattern without distinction, which is one reason the Hebrew Bible's angels are so difficult to separate from its people by name alone.
The tradition attaches a further significance to the choice. In the Kabbalistic reading used across most modern presentations, -el is referred to the side of severity or judgement and -yah to the side of mercy, mapping onto the two outer pillars of the Tree of Life. That reading is coherent within Kabbalistic theory, where the divine names are systematically assigned to the sephiroth and their columns.
What is not clear is that it explains the actual distribution. The suffixes are not evenly alternated, they do not fall into blocks, and no source states a rule by which a given three-letter group takes one rather than the other. The likeliest account is that the suffix was chosen to make each group pronounceable in Hebrew, and that the theological gloss was applied afterwards to a distribution that had been settled on phonetic grounds.
That is not a debunking. Retrospective interpretation of an inherited arrangement is a normal and productive operation in this tradition. But the interpretation is a layer, and it should be identified as one rather than presented as the reason the names are formed the way they are.