The radius rod bushings should be replaced when worn and they do wear, especially the 2 at the front of each rod. The radius arm itself does not wear, weaken or ever need replacement unless the bushings and washers were completely worn to the extent that the rod end opening at the rear or threads at front were damaged. I have never heard of this happenning. Why not ask them to explain further.

Curious why you have choosen to take your car to a dealer for service. Dealers are for recall or warranty work but you are generally far better to find a good garage that knows Volvos.