From experimenting in the Game Manager, it seems the answer to this question is "no". But I'd like to make sure.
Based on this, I need to decide if I want to store gameplay data about items in catalog item attributes, or in title data. I want to be able to update an item (for game balance purposes) and have it cascade to all players' inventories.
Correct - the attributes defined for items in the catalog are intended to be global. That way, you can change the values once at the catalog level, and have that apply to all items for all players.
The custom data on item instances are separate from this, allowing you to set up custom data or override values on the items in each player's inventory.
Is it accurate to say that when you use the API to get someone's inventory, that you aren't getting items' CustomData from the catalog, and for that you need to cross-reference the item id with GetCatalogItems?
Correct - that's what I mean concerning the custom data for the catalog and item instances being distinct from one another. You query the catalog to get the global data, while the item instances in the individual player's inventory contains the data unique to those instances.
