I think almost every bread bakers have had some experience with baking a brick due to under fermentation. However, pate a choux, the dough used for cream puffs and ecclairs, can rise very well without any leavening. Internal steam is generally thought to be the power for its leavening, but most artisan breads have more hydration than pate choux. So what is it about choux pastry that allows it to use with just steam, and have bread bakers ever tried to leverage it in their bread?
Pate Choux is a light and airy paste. Very different to a bread dough which needs some sort of leavening.
Well, I suppose you could check out tangzhong for a roux based method incorporated into breads.
Contrast the proportion of flour to other ingredients in a choux vs bread recipe and you'll probably have your answer. The image I have is putting a sumo wrestler into 6 inch stilettos and have him walk across a sand pit.
I think that the big difference is the eggs. Here’s a discussion from Serious Eats : https://www.seriouseats.com/choux-pastry