Update details have valid changelog in most cases. Also, the experience varies between distros.
Fedora handles update details in a different way. Refer this comment.
GNOME Software just displays what PackageKit get from its backends. (dnf backend on Fedora / apt backend on Debian etc). Refer below.
+-----------------+
| |
| DNF |
+-----+ (Fedora/RHEL) |
+-----------------+ | | |
| | | +-----------------+
| +----+ |
|GNOME Software | | |
| | | |
+-----------------+ | | +-----------------+
| | | |
| | | APT |
| +-----+ (Debian/Ubuntu)|
| +-----------------+ | | |
| | | | +-----------------+
| | PackageKit | |
+-----------> +----------+
| | | | +-----------------+
| +-----------------+ | | |
| | | ALPM |
| +-----+ (ArchLinux) |
| | | |
+-----------------+ | | +-----------------+
| | | |
| | | |
| KDE Discover +----+ | +-----------------+
| | | | |
+-----------------+ | | ZYPP |
+-----+ (SuSE/OpenSUSE)|
| |
+-----------------+