You have a point, but so does he. How many nonsensical comments have you seen online that are obviously the result of failing to proofread from start to finish after editing? You move a sentence from here to there, or rewrite or remove one, and the flow is broken, and it no longer makes sense. Writing and reading are--at least, within a single piece--linear activities. Creating a system for removing or rearranging sentences or paragraphs creates an exponentially increasing number of potential combinations, each of which would need to be proofread completely by a human or an advanced AI. Otherwise you'd end up with nonsensical articles and dumbfounded readers, and then the whole system would be thrown out.