@SleeprunnerInc The only reason FF14 does that tomestone deletion is to prevent having to store the data for every old tomestone + make UI for all of those old tomestones nobody uses anymore just because someone might still have them, because the deleted tomestones are part of a series of currencies that are constantly being introduced. If you want to equate SG to FF14 tomestones, the better example would be Poetics, since they're both evergreen currencies that never go out of rotation, and FF14 doesn't wipe Poetics from your character if you don't use them.
There's no reason for PSO to delete SG like there is for unused tomestones in FF14. Not to mention, they don't even expire in the JP version of the game, which shows that there's no actual reason it has to happen and it was additional work to do it like this.