I'm not an expert baker, but when you type "sourdough" into Google images, 99.9% of the results you are getting are photos of bread made with refined (white) flour.
As far as I know, you are never going to get a big, airy crumb with 100% whole wheat bread. Based on the article, I believe the Emmer flour used is not refined. The bread will always be denser than when using refined flour, but that doesn't mean it didn't rise properly. I bake whole wheat bread (100%) exclusively at home, and the crumb looks exactly like Blackley's.
Even if you type "whole wheat sourdough" into Google images, you'll notice that virtually all of them are only half whole wheat.
A few things to note here are that Foodgeek's bread is 80% hydration and still a bit dense, and that einkorn has a much lower gluten content than common wheat. The differences in hydration and gluten content will yield a denser loaf.
I bake sourdough bread and have had a starter in the fridge for several years now (way pre-pandemic).
What's your point? They didn't bake sourdough. They baked a different bread using an entirely different type of flour. So why are you expecting it to look like modern sourdough? This is a reproduction of an ancient Egyptian bread! And there are plenty of other breads that are even denser than this one (and delicious too, I might add).
