The layout is trying to make the best out of limited space. I built the tank last year with only Domestic Hot Water in mind. The tank is only 100 gallons, and the temperature probes have never shown much stratification anyways. If you're starting from scratch, I would recommend a bigger tank & maybe look at PVC stratification tubes (I think that's what they're called?).
As far as my setup the idea is that splitting it up into "zones" the hotter section of pipes are in different areas of the tank, so more exposure to cold section of tank and more even heating. In wort chillers it cools the entire bucket faster so same idea but with heating. I also feel like putting it in zones was the easier option to wind the coils. If you have a stratified tank, putting the coils in the cold bottom would be most efficient. At least that's my $0.02