After the lineups were exchanged at 9:15 and players start warm-up with their opponents, if a player doesn’t show up by the time 9:30, do captains re-do the entire lineups to default line 4 instead of defaulting higher line? To be able to do so, no line should begin the match until all the players get on their courts?
Yes you are correct. Play should not begin until 9:30 and until all players have arrived. If there's a default the lineups are redone to default line four and remaining players can be placed on any line. When the new lineups are exchanged players take the courts and begin play immediately with no further warm-up.
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