I think the argument was that curl is fairly feature complete (as shown by your list), is there really that many bugs in curl that require immediate attention?

"Featureful" doesn't imply "feature complete". They appear to release minor versions all the time.

https://curl.se/docs/releases.html

If you dig into them you'll see there's lots of features that aren't adding new protocols. But incidentally they added a new protocol in March (mqtt). You'll also see that the list of bug fixes is prolific.

https://curl.se/ch/8.19.0.html

Increasingly so, yes.