imo, The author of this essay does not understand the concrete problem that mathematicians are upset about. There is an idea that math [1] and coding [2] are human activities whose purpose is to achieve a certain kind of insight or mental clarity of things. The simplest description of this is by Feyman [3]. AI generated proofs short-circuit human understanding and therefore goes against the primary purpose. The declaration is calling this out loudly to reiterate that the purpose of the endaevor is not the generation and rewarding of proofs.
[1] "On proof and progress in math" https://arxiv.org/pdf/math/9404236
[2] "Programming as theory building" https://pages.cs.wisc.edu/~remzi/Naur.pdf
[3] "What I cannot create, I do not understand"