You seem rather aggressive so replying to you feels pointless and uncomfortable.

Nonetheless, the person writes, “ Math has been almost purely arbitrary”.

This is simply a misusage of the word arbitrary, which is a word with a specific meaning you can look up if you are unaware, since mathematics is (obviously) not arbitrary in the sense this person wants to convey, in part for the reasons I state. Humans are not choosing arbitrary logical statements to prove true or false.