So if someone wins the SP and then withdraws, the skater who finished 25th in the short should skate at the end of the event?
What would make more sense would be that if a skater withdraws after the SP but before the FS draw, then the skater who was 25th can be drawn with the 20-24 group, and the skater who was 19th moves up to the next higher group, etc.
Not sure if that works at events that don't have a draw but are now mandatory to skate the FS in reverse order, since the FS skate order is then known as soon as the SP results are posted.
Of course, if someone withdraws during the SP, then they won't have a placement and the skater who does place 24th (but might have been 25th without the withdrawal) does advance.