"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