Dogs, with their sense of smell and such, can assess the fecal matter's nutrition levels, and while they lack the gut setup to get the process started, they can certainly digest the bacteria. As semi-scavangers, they're not about to give up the easy meal...
I'm not convinced they smell nutrients so much as eat everything they can just in case. That would explain the plywood, coffee cans, rocks, leashes, shoes, license plates, aluminium foil, walls, dog booties, straw, books, electrical cords, and in one case small box of thumb tacks I've had dogs eat.*
*And I'm differentiating eating from boredom chewing here. all those items were consumed and found in poo.
Also funny story, since this thread has been going on, My roommate, yesterday, read his email and told me "My Nephew has to get a
fecal transplant. Have you ever heard of that?" and I was able to reply: "Oh Yeah, they do that to rebuild the gut's bacteria." APS: Making us seem well educated one obscure medical procedure at a time.