it's about dependencies, large projects like gstreamer depend/use a lot of other projects
when there is a change in one of the upstream projects all packages using said project get rebuild with the new change hence build numbers are used
you can see that any opensuse package comes with a large numerical string for example
gstreamer-plugins-ugly-1.12.5-lp150.1.1.x86_64.rpm (the lp150 is a new addition meaning it's a leap 15.0 package)
the string includes the version number 1.12.5 and the build number 1.1 when ever something upstream is changed and the package rebuild the build number will increase and you will be notified of an update
a lot of multimedia packages get rebuild daily and I usually get a few dozen packman updates on my Leap box every day most of them are identical to the packages they replace as they're just new builds of the same code