One of my research colleagues, the systems engineer Duane Hybertson, suggested I not use this phrase. I think he is correct. He suggested EVIDENCE FOR ISOMORPHY. That very much more limited phrase frees us from trying to achieve the unachievable and from the hubris of parts of science and engineering.
It is also much more in line with current philosophy of science positions and the consensus of working wet lab mentors who lecture each other and their graduate students that science never actually proves beyond any doubt anything as much as tests it over and over until there develops a level of confidence. It is a crucial part of learning the scientific method to always look for negative evidence against your favorite or personal hypotheses. Otherwise you are not doing science; you are doing polemics.
Consequently, we do not say we have definitively proved that an isomorph exists in every systems as much as collect lots of evidence that supports that its presence is important to many successful systems. I am tempted to call them universals. But they are not. They are widespread contributors.