Speculation:
Owner: "Hey, what's with this wasted space above the ramp?"
Architect: "Umm...a roof?"
Owner: "People like pools, let's add a pool."
Architect" "Ok. I'll call the engineer."
Structural Engineer: "A pool!? Now? The building's almost finished! Ok...something kind of like this? If you like it I'll detail it tomorrow." (Sketch is just a blob with no dimensions, rebar, etc.)
Architect: "Contractor, how much will this cost?"
Contractor: "A zillion dollars."
Architect: "Ok, we'll do it. What else do you need?"
Contractor: "We got this..."
Structural Engineer: "I guess they decided not to put in the pool..."
Fast forward 4 years -
Process Server: "Mr. Engineer, you're being sued for the structural failure of the pool you designed."