Yes. Indeed it is. I would add "And it is an invented language".
Max Tegmark's idea is nonsense. It is a Platonistic delusion of a kind that seems to be shared by many mathematicians. A mathematician correspondent of mine has told me that "Some people who discover mathematics in their young age immediately tend to see it as a reality on its own. These people usually become mathematicians. In my experience, every mathemacian is a Platonician. I don't know a single one who is not." I believe him. For example Roger Penrose's book "Road to Reality
" supports this belief.
Are we not all susceptible to delusions of a similar kind about subjects that we are proficient in, admire greatly, or that fascinate and mystify us? For example that polemicist Richard Dawkins has written an entire book about one such delusion, namely that of the Theist variety. It seems to me that reality is mysterious enough withot adding a mathematical dimension to it.