it shouldn't have worked, but...

I was going to feed the pet but I'd run out of AP flour and went out to get some. Back at home, I saw that I'd bought the white whole wheat flour (KAF) by mistake. Didn't even know such a thing existed. Read up on it at the King Arthur web site, and they recommend using it for cookies, muffins, etc., but there's no mention of breads. Not good. I looked into it a bit more, and it's a low protein flour, which is why it wouldn't be good for bread. But I was curious, so I separated some of my sourdough starter and fed it with this flour. Fermenting seemed OK, but it didn't rise much. Not a surprise. I fed it a few times more, decided it was time to try to bake it into bread. I incorporated some bread flour into it and let it rest about 40 minutes. After the autolyse, it looked very wet. So I added some more bread flour, until it was a respectable soft dough consistency. Folded it twice at 45 min intervals, then put it in the fridge to develop overnight. Next day I divided it into two, formed smallish boules, and let them proof in baskets lined with kitchen towels. After a couple of hours they were pouffy, but hadn't risen much. It looked like further proofing was not going to help. (How do I know this? I have no idea.) My oven was already preheated to 500 F with the baking stone in place. I didn't want to risk placing the loaves directly on the peel, because they still seemed not sturdy enough. So I lined the peel with parchment paper before I up-ended them. Sure enough, in 5 seconds, they looked like ciabatta. Not very hopeful, I stuck them into the oven. There was almost no oven spring, but again, it's not surprising given the qualities of the flour. I let the loaves cool overnight and cut into them the next morning. Surprise! They were not bricks. In fact, they were quite light and hole-y. And they weren't too sour. They looked and tasted better than most store bought 'artisanal whole wheat'. Definitely edible. Not nearly good enough, but definitely edible.

I'm confused. Low gluten flour, therefore not much rising, but still pretty good crumb. Shouldn't it have been dense and heavy? What do I know.