Indeed. I find this to be a rather strange opinion; in terms of the language itself, I can’t really say one is better than the other for expressing mathematics.
As long as we're sticking to core language JavaScript is not the right answer as the only numeric type, Numeric, is a IEE-754 "double". For lots of maths however integer semantics are better suited.
Python has arbitrary sized integers in the language, which even improves the usefulness.
Of course libraries and extensions could eventually help.
And python doesn't? It has bignum, is that inferior? It is also arbitrary precision. Seems like to claim javascript has "sufficient" numerical properties would be better than claiming it is far superior to python. To do otherwise seems like FUD
Thus I claim the Python approachbiss till better in that specific area.
I don't know Deno's source for their claim. Certainly relevant is what area of Maths you're looking at. For instance looking at reread rations for vectors and matrices might be relevant for different maths problems. The functional approach in some of these things also might be interesting for some Maths problems ... broad topic :)
It would be nice to read a rationale about this.