I have heard/seen that; I didn't know if it was official. Basically, like half the NPC groups have the pearl as a jewel, and so most of them can use that, if they don't mind inter-group confusion.
Total lane swerve, but I think that in Tri Delta, the pearl specifically symbolizes the new member, while the pine tree symbolizes the collegiate member and the pansy the alumna member. More here.
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