BBA Pain de Champagne + Levain / Mysterious Results

Prior to the one-loaf mystery result of my last post, the openest crumb I've gotten from the BBA pain de champagne recipe was a few weeks ago when I modified the recipe to use a dose of the KA levain du jour (dried levain starter), the mild version. I basically made the sponge from this starter as per the instructions that come with it, but made sure the amounts of eveything in the end would total to the same as BBA recipe using the pate fermentee as usual. A second alteration I made was to put most of the rest of the flour (including the whole wheat) into a soaker. The end result was this:

Because I'd changed two different things at once, I wasn't sure if it was the levain or the soaker or both that produced the opener crumb. So I did another batch a few days later with no levain, but with the soaker. The result was the typical crumb I get from this recipe (which has improved a bit over time, as I've pushed the hydration a little, improved my kneading technique, and switched from my somewhat alkaline tap water to bottled water). Interesting thing about this batch though. It had the slight tart tang to it, just as if I had used the levain! I assume that by chance either my pate fementee or my soaker picked up some good beasties...perhaps there were some floating around left over from the levain. Maybe I should start making a point of not cleaning my kneading board!