I think you may just be confused about the specifics of "adopting it".
Python 3 has been packaged and co-installable in Fedora for many years, and likewise a large number of Python 3 libraries are also packaged, and Fedora even put in quite a bunch of effort into tracking and increasing that number via porting efforts. And thanks to all of that, things are now getting ready to abandon Python 2 for the most core parts of the system itself.
So it's not like those six were spent idle, rather they were in the process of "adopting it" for much of those six years, and this is simply another milestone in that process.
If you were a user of the system and wanted to run something against Python 3, you could do that for a long time now. I've written plenty of Python 3 on Fedora systems using nothing but system packages.
Python 3 has been packaged and co-installable in Fedora for many years, and likewise a large number of Python 3 libraries are also packaged, and Fedora even put in quite a bunch of effort into tracking and increasing that number via porting efforts. And thanks to all of that, things are now getting ready to abandon Python 2 for the most core parts of the system itself.
So it's not like those six were spent idle, rather they were in the process of "adopting it" for much of those six years, and this is simply another milestone in that process.
If you were a user of the system and wanted to run something against Python 3, you could do that for a long time now. I've written plenty of Python 3 on Fedora systems using nothing but system packages.