Where does the default value for WIP Supply Type come from?

Summary:

Where does the default value for WIP Supply Type come from? The WIP Supply Type is set to null on an item template but when creating the item it's populated with 'Assembly Pull'. There's no parameter to the Inventory Organization nor the Plant Parameters that this value could be coming from so it's unclear how the value is being set in PIM when the item is created. I'm posting this here and in the PIM area as well.

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Version (include the version you are using, if applicable):

22D (11.13.22.10.0)

Code Snippet (add any code snippets that support your topic, if applicable):