Antimatter Civilization and Krypton Gold Civilization discovery.
Puff-back wave is not a common weapon, but a very special one with extremely strict conditions for use.
Some less crucial conditions can be set aside; among them, the most important condition is the need for a stable Cosmic Space as the foundation.
In other words, puff-back wave is actually a special weapon developed for the Universe, aiming to exploit loopholes in the Universe's own rules and must be used based on the integrity of the Universe.
This is similar to a scientific team needing to create waves, which would require sea water. Without sea water, it is impossible to generate waves out of thin air.
