Much of pipe smoking is subjective. Tobaccos vary significantly as do the pipes in size, shape and bowl geometry. I don't think there are many who actually recommend dumping the last 1/3 of the bowl. They may recommend it because their own smoking preferences won't allow them the ability to...
I strongly prefer a 1/8th to 1/4 bend max. I have a reasonably eclectic collection but my shape preferences tend towards Bulldog, Rhodesian, Hawkbill and Billiard. Those probably make up 75% of my collection.
Perhaps it wasn't sealed properly at the factory or perhaps the tin was jarred causing it to loosen. I've seen it occasionally with circular and square tins but it has been rare. If the tobacco was still in good shape, I wouldn't worry.