The posts in your first screenshot are already deleted - they are soft deleted posts. If you click on the "Show" link next to them you will see the soft-deleted post and the checkbox.
Admittedly it would be useful to have the checkbox visible on soft-deleted posts without having to click on "Show" just as it was in Xenforo 1.x as it means that further moderation actions can be carried out without lots of clicking on "Show" links first.