Are you sure? CS6 still shows up in my Creative Cloud app (which I upgraded moments ago, by the way).
Your point is that PR/EN CS6 is still available, and that is true.Your list is of the "installed apps" section and indicates that it is already installed. The poster indicates it was uninstalled and he should be looking in the "find new apps" area. Many users appear to be continuing to install PR CS6 with EN CS6. But others are having problems (as some have all along).
A new problem appears to be that users seem to believe they have to uninstall PR CC in order to add PR CS6. And some odd errors have added fuel to the fire.
The errors referred to by this user were probably no more than trying to dynamic link from PR CC to EN, which, of course, does not work.