Well I seem to have answered my own question, the credit card + *G allowances cannot be combined:

"The primary cardmember and one traveling companion on the same reservation are each eligible to receive their first checked bag free; authorized users are only eligible if they are on the same reservation as the primary cardmember. To receive first checked bag free, the primary cardmember must include their MileagePlus® number in their reservation and use their MileagePlus Explorer Card to purchase their ticket(s). First checked bag free is only available on United- and United Express-operated flights; codeshare partner-operated flights are not eligible. Service charges for additional/oversized/overweight bags may apply. Members who are already exempt from other checked baggage service charges will not receive an additional free checked bag. Chase is not responsible for the provision of, or failure to provide, the stated benefits. Please allow 2 weeks after account opening for your first free checked bag to be available on your United reservation. For more information, please visit www.united.com/chasebag."

https://creditcards.chase.com/credit...aspx?fcsplit=1