But why does it matter what you practice when? If you think your LP or FD needs more practice than your short, it's just your short that will pay the price if it hasnt beenracticed enough. It's not like gymnastics for example where spending extra time on beam means another competitor can't use it. You can be training your SP while I do my LP and there's no conflict.
Basically it's about which music is played. Skaters who are practicing to the music being played get right of way.
At competitions, there are often official practices designated for short program (or CDs/ODs, before the short dance combined them). These practices may be scheduled to be shorter than other official practices later in the week designated for free programs, e.g., 40 vs. 50 minutes. Each skater gets their music played once during the official practice, in a preset order.
At the shorter practices, there may not be enough time to play everyone's long program, so they are not given that option. Their short program music will be played once, and they either skate a runthrough or partial runthrough to their music when it's played, or they don't. But they don't have the option of playing their long program music instead.
For longer practices that are scheduled before the short programs, the skaters may be given a choice of which program music they want played when it's their turn.
Obviously for the practice sessions scheduled after the short program has already taken place, everyone will have their long programs played, and the sessions are scheduled to allow enough time for that to happen.
For dance practices when there were compulsory dances and everyone skated to the same few ISU-approved music selections, in the CD-specific practice session or beginning of CD/OD practice, all the tunes that were scheduled to be used in competition would be played once. Several teams could skate the same CD at the same time. Anyone who was not working on that CD would need to yield right of way to those who were.
For the music that belongs to a specific skater or team, that skater has right of way, but it doesn't matter what the other skaters work on when their own music isn't playing.