I am not sure I understand, on a three pase board you may use any one of the 3 phases to power 3 single phase loads or 1 three phase load, ypu may on larger boards have a mixture sone 3 phase devices and some single phase devices for exalmple on a commecial board you can have some 3 phase fryers, combi ovens, and pizza ovens then lots of singles rings circuits mixers etc etc so if say a 3 phase oven was not heating up properly you check that all three are present at the board then check at tje oven although rotation is unimportant here, however if it was a motor then how the phases are connected is important, but you would only be concerned if you had replaced the motor or had the terminals off for some reason as it would try to run in reverse so thats where the rotation check IS important
Pict