I don't think it's a terrible idea on paper. Many who booked the 9 day, did so for that particular itinerary. But this is a good option because it hits two 7 day cruises. That gives two different groups of people a chance to turn their 7 day into a 9 day cruise. That would also give B2B passengers an afternoon to explore Vancouver between sailings plus a chance to visit Seattle which isn't a normal DCL stop. I agree that offering this right now does seem somewhat pointless. But I guess there's no harm in selling the rooms if people are willing to book them as they hold out hope for a miracle. Worst case, it's just another round of refunds or credits. If someone books it, they have to know that's the most likely outcome.
Incidentally, we did a 2 day in California for Mother's Day a few years ago. It was ridiculously short but we got to have some nice meals, see Frozen the Musical, Disney Dreams, Avengers Infinity War and spend a nice weekend together as a family. The ship went to Ensenada and I doubt 1/4 of the people got off the ship because it was so short. So the port day felt like a sea day because there were still a lot of onboard activities. I don't know that I would do it again but I don't hate the idea of adding it to a longer cruise. In fact, if I were on one of those two Alaska sailings, I would definitely consider adding this trip on to my itinerary because it would be something different. Maybe they are exploring interest for future cruises while taking advantage of 2 days where the ship was going to be sitting empty?