cURL also offers paid support and also paid access to the rock-solid (LTS) version, with guaranteed response times, and the blog post states that there's still people to respond to these.
In most cases this is extremely impractical.
Then you send the patch upstream, they incorporate and maintain it for you. Congratulations, you just FOSSed.
Firing patches upstream is still adding burden to the (likely already over-burdened) maintainers.
In an ideal world, if you want a patch upstreamed, you would be contributing to upstream maintenance (or at least donating to the upstream maintainers)...