Have you reviewed the code? What were the problems with it? Where did it do things better than you'd expect of humans? Have you compared the effort of making changes to it to the effort required for similar, human-written software?

I don't think anyone says it's not possible to get the LLM to write code. The problems OP has with them is that the code they write starts out good but then quickly devolves when the LLMs get stuck in the weird ruts they have.

Far short of a proper review, however I have scanned the code. Bear in mind this was a purely personal project, never intended to see the light of day and initially just done to create a small but operable chunk of dbus/blueZ glue code for another project.

I have no doubt that a C developer with sufficient knowledge of dBus, bluetooth, the HRM profile and linux could have written the C code in a day. Adding the HTTP server again would be easy if the developer also had experience of that (n.b. there was a minor compiler error when I tried it on another system due to a slightly different version of libmicrohttpd). Adding the API would be straighforward (but tedious) and similiarly the web page (the web page was an one-shot after Claude wrote the API, vis. "Create a web page to display a real time plot with history using the API").

So overall I'd answer that that human developers would could have pulled that off in a day are few and far between (and likely to cost a lot more than $25 plus a day of my time).

And do I think the code is good enough? Yes, more than good enough. I could take it and run with it, against that because it ended up 100% AI-generated I feel a bit like leaving it as a monument to "pure AI".

After all, I never intended to release it - it was this thread that made my throw it up on Github as an example for the OP.