From https://bnadventure.com/self-guided-tour-in-the-peaks-of-the-balkans/:
The trail avoids the classic peaks of the Balkans trail as the situation in the mountains has changed since the trail was established. This itinerary takes that into account and provides the best views and best experience.
That sounds like there may be a problem with the classic peaks of the Balkans trail. How has the situation changed? Has the trail been abandoned in parts? Is it the opposite problem and is it too busy? Has it been blocked or made less interesting by new developments? Or is there not actually much of a problem at all?