In steady-state conditions Proviron should not have much influence on free DHT unless it is significantly affecting 5ar activity. But I would expect a reduction, if anything, due to possible negative feedback of higher DHT-like activity. Otherwise Proviron is just adding on to existing DHT activity. A widespread misconception is that a real or virtual (Proviron-driven) reduction in SHBG affects free hormone levels. This is not the case when a new equilibrium is established.
On the other hand, maybe you're suggesting the transient behavior is driving the subjective results. As Proviron levels rise there is some displacement of SHBG-bound DHT, temporarily increasing free levels. However, as Proviron falls free DHT decreases, even going below baseline before a return to the original equilibrium.