I don't understand this either. That is why I sent them an email last night, expressing my disappointment.
I emailed them too, unfortunately I think I came off a little whiney in it. The points I tried to make were 1) they should have made this change with cruisers who have not been allowed to online check in yet, 2) lines outside are going to be horrendous (especially in August heat), 3) how are they going to keep people outside seperated by those who have an actual arrival time vs. those who just show up, 4) I made a plea for those who were not able to book Palo online and were showing up early in hopes of securing a reservation onboard early