You are correct that EndeavourOS is a rolling release. In that sense, you never have to ( and never really do ) “upgrade” to these new “releases” since you are essentially always using the latest software.
The releases do two things:
1 - they provide updated install media that are closer to the current repo contents so that upgrading after install is a smaller and more reliable operation.
2 - they provide an opportunity to change the system defaults. For example, the move to dracut. If you installed a couple of years ago, you can upgrade all your packages but you will still not be using dracut ( unless you make that change yourself ). Everybody that installs EOS now will use dracut by default. That is true of other things, like this change to KDE for the offline install.