I think that you will find that just about any rest period in the preparation of the dough will make the dough softer and easier to work with. That is the theory behind the concept of autolyse. In your case, by leaving out the salt during the rest period and adding it later, you in effect used an autolyse except that you included the yeast in the autolysed dough (in the classic autolyse as Prof. Calvel advocated, the yeast is also added later). I remember having a discussion with Evelyne Slomon over at the PMQ Think Tank on why professionals did not as a matter of course use rest periods during the preparation of the dough (although a few, mostly in Italy, used a riposo at the end of the knead). She agreed with me that it was very uncommon in the professional ranks in the U.S. but was being adopted by a few professionals who were trying to make a more artisan product.