once you GIVE a quilt it is no longer yours to decide how it is used-or even whether it is used. you gave it away-
maybe they like the back better than the front- just because you like one side over the other doesn't mean everyone will- we all have our own tastes- maybe the one on the bed is covered to protect it- maybe you should be happy it's not in a garbage bag in the attic or basement- or in a goodwill box.
no- i do not think you should say anything- it is no longer yours to decide how it lives- unless you are asked about how to care for it - you should just be happy they like it well enough to use it at all