I think the point was that mathematics relies on a small set of postulates from which you can derive everything else. Changing a postulate results in a separate system. The same is true in programming languages, but the number of postulates is very large compared to mathematics to the point that their utility is greatly reduced. And also there are so many languages each with its own postulate set that it's really inelegant when compared to mathematics.

Another way to put it is, learning the postulates for langx doesn't provide enough value for many to be worth doing.