Did you read the rest of his post? He's not basing his choice on his sneaker size - he specifically mentioned his size in the Indy boot, which he says fits great. Generally
speaking, most people wear the same size in the Trubalance and Barrie lasts.
The thing that doesn't make any sense is how 9.5D is tight, but just one width up in 9.5E is much too roomy. There's no size in between those two, so if neither of them fit then the boot probably won't work for OP's foot. Maybe try a 9E? Based on the description of how the 9.5E felt (good in width but too long), a 9E may work. If a cordovan boot feels tight at first, it's not going to stretch all that much with wear.
I was thinking a 9E would work as well. Just wanted to see if anyone else had experience with this specific boot because the cordovan seems to create a different fit for trubalance boots