Not necessarily. Have you ever played Monopoly where an opponent held Park Place and you land on an unowned Boardwalk? What do you do -- one option is to buy it, mortgage it, take your $200, and let it lie fallow the rest of the game since it's rarely landed on just so your opponent can't start building homes/hotels. Another is to buy it leave it active, get $50 every once in a while.
Just saying there are options, and one of those is to keep the patents and shutter the phone biz. I don't think there is a single common sense answer as you suggest. Could logically go either way, though keeping the biz ongoing is the harder of the two. Either way they keep the patents out of Apple's inventory.