I bet the author discovered the problem during an AI coding session. The "mathematically sound" comment sounds like the AI did some deep dive into a possible corrupted private key before checking for a missing public key. Maybe it's a claw-type system that automatically publishes a blog post when something interesting happens. Either way I flagged it.
So let me see if I understand this. Something apparently has recently changed at GitHub that will break a perfectly valid way that clients can configure ssh. Someone hit that problem, tried a bunch of things to diagnose it, figured out what is broken and a workaround (switch to another perfectly valid way to configure ssh on the client).
Rather than going into detail on all the things they tried to figure that out they went straight to concisely explaining the workaround.
They then briefly explain why those two different ways to configure it lead to different flows on the server.
There is absolutely no question that this will be useful to anyone how hits this problem and has this turn up when they search for help. There is nothing in the writing that, if this had been written in 2018, any reasonable person would find to criticize.
But because you see one bit of phrasing that you think might be LLM influenced you flag it?
To be honest, the "mathematically sound" is a widely used jargon used in many academic fields (physics, mathematics from first hand experience). It is also more meaningful than people who would use "nice function" to mean a function that follow some criteria in their head (and you would need to guess what these will be).
This isn't about an academic issue though, and who would actually state their RSA key is mathematically sound except in the case that they're performing some research in the field? The point the parent was making was that it was obviously written by AI.