Bulging brass from semi auto pistols is nothing new. Especially in Glocks. Throated pistol barrels all bulge brass right at the base, which is very difficult to resize. Especially in full power loads. This brass cannot be brought back into spec by a regular sizing die, because it can't reach the all the way down to the rim. A push through die can and does. It is the only way this brass can be properly resized.
Many times when these push through dies are not used, the result is brass that will not chamber, and the gun will hang up as a result. The push through die makes reloads with this brass fully dependable. That is the goal every reloader should be striving to achieve, regardless of what he is reloading. Using a push through die when resizing full power loads in .40 S&W, is like using a primer pocket swaging tool to remove the crimp in military brass. It's another step that needs to be taken to make reloads with this type of brass fully dependable. The only other option is to throw it away. That's like throwing away money.