You only get one set of choices per DM qualification. It makes no difference how early or late in the year you qualify. You qualified for 2018 status and thus 2018 choices benefits and you have already picked them. You do not get another set of DM choice benefits until you qualify for 2019 status and thus 2019 choice benefits. No, it is not a mistake. Why should you get two sets of DM choices benefits when you have only actually qualified for DM once?