I've noticed that aluminum squeeze tubes have a fold at the end. The fold is not the seal of the tube, as I can unfold and see the seal on the very end of the tube once unfolded. Wikipedia states that
Aluminium tubes generally have the far end folded several times after the contents have been added. The tube is thus hermetically sealed and nearly germ-free due to the high temperatures during the production process. The inside of the tube can be coated to prevent the material from reacting with the contents.
I don't understand why the 2nd sentence follows from the first, especially in my case where the seal is not the fold, rather it looks like the seal was made, then it was folded. Shouldn't the seal be enough to hermetically seal the tube?
Why are aluminum tubes folded at the end? How does the folding relate to hermetically sealing the tube?