When I use GetUserInventory, the items in the result do not include the original custom data that was part of the catalog item. Not sure if it just isn't copied over or is just excluded from the result set.
If it's intended that it's not copied over when the items are granted, then that poses an issue for me since that would mean I would only be able to grant items using Cloud Script (so I can copy the custom data manually), and thus couldn't grant bundles, tables, etc.
Maybe I can make a repair routine that goes in after a grant and loops through and copies over custom data for items without it, but that's not ideal.