Not that I'm trying to defend CX at all but CX will and do upgrade as required. All the check in staff need to do is follow the policy correctly, something they don't always do.
I instead have
never seen them do so. A little sad, because it is a cheap way of fostering goodwill. It is particularly galling when the airplane leaves with empty business class seats and staff travelers are left on the ground, when a simple upgrade, if not to the staff traveler then to a y-class frequent flyer pax (in order to free a seat for the staff member), would make everyone happy.
I am a little ashamed every time I get upgraded on more staff-friendly airlines (BA, AF, KL) as I know I will never be able to reciprocate for them as long as I fly for CX... another lost opportunity.