Understandable why this speculation would come up, but they won’t converge all their units on Byranks and ill tell you way. For the simple reason that they can’t leave Kiev undefended as well as the fact that they won’t have nearly as many units as you by blobbing together.
Keeping a blob of units is an incredibly newb thing to do as it doesn’t accomplish the goal of your playable nation. And the Germans won’t be keeping this blob they’ll divide it evenly to overwhelm the Soviet units. And if they blob together i absolutely welcome that because if they do then all those units are dead. The luftwaffe as well as every unit on the Eastern front will move in and destroy the Soviet presence in Bryanks