I was attempting to make what should have been a simple system,

ignore data being loaded when it's from the player being restored, but not ignore it when it's the first time you create it.

I used the OnPlayerDataUpdated's Info[] output, and found that the item for "Added" would always be called on world load. Similarly, the item for "Restored" was being present even when it's the first time you are in the world.

I ended up making a workaround to solve my case, but I'm fairly certain this behavior in the first place is a bug or an oversight due to how rare data needs to be "added" over "restored".