The copper pipe attached to the trap attached to the cast iron waste is the drain for the dishwasher. Aside from contadct of dissimilar metals and not being installed to the manufacturer’s recommendations, just what is the defect here?
It doesn’t look like contamination of the cabinet from siphoning would be a problem.
From the looks of the Bell&Spigot, it’s not a new house.
The drain looks like it is physically attached, wonder how it works without the air gap?
The trap is actually made of this brass and chrome plating, so dissimilar metals might not be an issue.
Surprise a plumber would use a regular copper Tee in lieu of a wye.
Looks like they might have used the cast iron pipe sewer cleanout to hook it up also.