My understanding is that salt inhibits the development of microbes (like lactobacillus) that assist the yeast in breaking down the gluten, so a long autolyse can be kept in check by the addition of salt and/or cold temperatures, without worry about the gluten degrading to the point of losing structure.
I vaguely recall seeing something (maybe by Vanessa Kimball?) saying that the acidity in the starter can inhibit autolyse. Not sure how that works if you're making a sponge.
My understanding is that salt inhibits the development of microbes (like lactobacillus) that assist the yeast in breaking down the gluten, so a long autolyse can be kept in check by the addition of salt and/or cold temperatures, without worry about the gluten degrading to the point of losing structure.
I could have that wrong though.