Rigid pvc--aka "hard pipe" is only recommended for long STRAIGHT runs 'cuz any bends that are greater than the pipe wants to bend require cutting the pipe and inserting inline radius fittings, every one of which is a fitting that can trap waste and TP, and where sea water minerals and salt can build up. More than one or two of those creates more problems than it solves. That hard PVC is a lot cheaper than top quality odor permeation proof hose is its only advantage.
Edit: I just read the article. He could have eliminated both the 45 and the 90 in the first photo by simply moving the inlet fitting on the tank to the top of the tank (apparently he's never heard of the Uniseal, which would have made this an easy job). I could only see enough of the tank vent line to see the two 90s in it and it also appeared to be the "standard" 5/8". So while he may have eliminated permeated hoses as a source of odor INside the boat, it's unlikely that what comes out the tank vent will be odorless. And there were several other things that he made a lot more complex than they needed to be.
--Peggie