I don't do pure math, but I write the occasional theory paper, and this resonates. So much ends up on the cutting room floor--usually you proved the key result three or four different ways before finding a proof that is actually incisive/aesthetically pleasing/whatever to justify signing your name to it sending it out the door. Also most mathematicians are extremely averse to even saying something that's incorrect, let alone putting in print. There's ton of sanity-checking and trying to break your own result that, again, is rarely if ever mentioned in the final publication.