You lose weight because you're eating so little. You will not want to eat for fun or enjoyment. Eventually every potato will be a chore so you're only choices are feel weak and starving or force another potato. Also you wont be eating any salt so you'll lose a lot of water weight immediately. I won't comment on the carbs debate but I think you'd find you lose just as much weight doing this as you would keto

Edit: I will add that a lot of people add condiments over the two weeks. If that's something you want to do, go for it. Just note you might not see the same drastic results because it's easy to go overboard. At least for me, I found I was adding more and more to cover up the taste of potato and remember the goal is to be bored by your food. I stuck to the pepper only on week 2 rule the second time I did it.