Boule formation and gluten tightening

Whenever anybody describes boule formation just before setting dough to proof, it is claimed that the glutens on the outside are tightened so that the baking loaf will hold its shape.

What bothers me is that I can't see these glutens remaining tight through the end of the proofing. Certainly they relax a lot whenever the bread is resting during stretch and folds.  I submit what what is actually happening in this step is that the tiny bubbles near the outside are popped, and it is the resulting the lower density of bubbles that gives the (eventual) crust its resilience.

What do you think?