So the specific story I was referring to was an obscure security fix to their equation editor in binary, rather than source. The impressive bit wasn't just editing a binary but patching a bunch of security holes without altering any other instructions: https://blog.0patch.com/2017/11/did-microsoft-just-manually-...

That said, I'll bet this kind of 10x programming is genuinely rarer these days. Not because programmers have gotten worse, but because new tools and relaxing hardware constraints make this sort of near-metal optimization less necessary and less valuable. The sort of data-reuse hacks that made e.g. Pokemon Red/Blue possible would just be a pointless headache today, so those same skills are getting spent on code golf instead.