In a surprise move, Ubuntu developers have agreed to stop shipping Flatpak, preinstalled Flatpak apps, and any plugins needed to install Flatpak apps through a GUI software tool in the default package set across all eight of Ubuntu’s official flavors, as of the upcoming Ubuntu 23.04 release.
You are confusing package maintainers with upstream developers. They are not the same people, and this is by design in most distros, so that maintainers provide a second pairs of eyes, provide security fixes and sometimes remove trackers and similar “features”.
No, I know what a software maintainer is. In many cases, the developers writing the software also provide builds or at least build scripts. So they’re also packaging it.
You’re obviously correct that the people maintaining packages in distributions don’t have to be, and often are not, the same people who maintain the packaging scripts in upstream repositories.