Hey @JJasperr
Yes, that’s right - productVariantUpdate is available to be run as part of a bulkOperationRunMutation. InventoryQuantity does not exist on the productVariantInput, although InventoryQuantities does.
However unfortunately, Inventory Quantities is a create only field(docs) and so it wouldn’t work with productVariantUpdate as part of the bulk mutation.
To update the inventory quantities, after creation, it is looking like you would need to use inventoryBulkAdjustQuantityAtLocation mutation - there are some docs here. Hope that helps!