Nice work and a big 'attaboy for being detailed in your work.
The hole in the cabinet for the electrical box is just so very typical for RV construction, Like you said, it would be so easy to have a jig to cut the hole neatly to a standard size. I've seen pictures on the Forum where an owner removed the tub or shower pan and discovered a 12"+ hole to run the plumbing. The hole was left open to the underbelly and could only have caused problems in the future with rodents, humidity, or water infiltration.
Good on 'ya for posting the pictures and calling out these hack jobs by the RV industry
