Specs and “as built” are two differnt things.
They probably use nearly identical plans for all stores built using a certain layout, i.e. 110-120k SF Super WalMart with garden center, 85k SF regular Walmart, etc for a period of time until change out equipment or layouts annd use those new plans from that point forward.
It is possible they had some major flaw in the plans or a specific contractor make a huge mistake. A 6 month closure implies they will probably be redoing the entire system, assuming the plumbing reason is accurate.