Hardly, there are sets of axioms where 1 = 1 which already show this in exquisite detail.
But I'm willing to believe I'm simply naive here. You say there is some set of axioms which prove that 1 = 1. Are those axioms not agreements? Since you seem to be familiar, what are those axioms?
There are sets of axioms where 1 = 1 is false, different sets where it’s undefined, and finally sets of axioms where 1 = 1 is true.
However, for a given set of axioms there is no choice and nothing to agree upon. That’s what makes math universally true.