Don't know what so hard to understand about it.
In a world where you have COS's, High end stickburners, pellet poopers of all stripes, reverse flow this and that's- there is is the UDS. As stupid simple a cooker as a fella could ever want. Bone stock- it just works. Bling it out-and it's yours. ATC's or ball valves- doesn't matter- all good.
Fpr some years now- every time some posted "what cooker should I buy?", "build a UDS" was an answer- and it was not totally in jest..
I can't ever see a time where I don't have a UDS.