Personally I agree that using core at the same time with 6 as version number was not the best choice.
In software development different versions of the same product first should imply backward compatibility and foremost an increase of the number of features available.
My opinion is that powershell core goal at this stage is not meant to replace powershell 5.1, but just working side-by-side. Otherwise the default choice should be an in-place upgrade or a windows update release.
Try this one-liner
get-command | measure
It will show you at glance that powershell core has almost 10 times less cmdlets 425 vs 4009 ( your result my vary by the number of module loaded). Similar comparison for the get-module.