actually looking at the website I don't think it's specific to the BOGO promo. Looks like even for cash stays you need a 3 night minimum stay, and I think their system won't let them book 2 nights paid + 2 nights free to get 4 nights total, which means they have to book 3 nights paid + 3 nights free=6 nights. Just guessing, maybe too shortstaffed to clean the rooms for 2 night stays. this is a change as of yesterday I believe