I think what you are referring to is Estrogen rebound from stopping Nolvadex.
Nolvadex is a SERM, and works by blocking certain E receptor sites in the body, it does not stop the actual conversion of T to E. So what happens if you are not using an anti-aromatase and using Nolva only, is when you stop taking the Nolvadex, there is still alot of E floating around the body, and that can aggrevate gyno symptoms. IT does not happen to the majority, but is possible. IMO, if you taper off the Nolvadex, you should be able to avoid any problems.
Does this hold true for Proviron...."No", as it works through a different mechanism, like an anti-aromatase.