I booked a flight for 2 of us without hold luggage some weeks ago but last week decided to add just 1 hold bag onto the booking.
Having just looked at the booking and charge again, you do only get charged for 1 bag but either passenger can have that bag.
Both boarding cards state hold baggage 'yes' but obviously because it was only added to the overall booking and not the individual, the option needs to be available on both boarding cards in case 1 passenger doesn't travel for instance.
It was your thread that prompted me to look but I certainly wasn't charged for 1 bag each... Just one bag each way on the booking itself.