They are symmetric before endgame, and those lengths are correct. But that rule only works with across clues, because of the way numbering works.
Imagine 1d in first column was 4 letters and 2dn in second column was 3 letters. By symmetry the last answer in the right column will be 4 letters and in the second right column 3 letters. But in clue order the 3 letter answer will be last because it starts further down. I hope that makes sense