IMHO, the whole lower ball joint arrangement is WAY over engineered compared to some other cars. The bolts bolting the lower ball joint on for instance are massive and the balljoint flange is equally massive for this little car. The way those four bolts bolt up into the bottom of the strut is a very stout arrangement, doesn't scare me one bit to reuse the bolts as long as they are NOT corroded (which is something the engineers may have been concerned about, being from a cold climate) and they were always properly torqued in the past (not over torqued). They are not torque-to-yield or anything like that either. The whole lower ball joint setup on my Alfa 164 is way less stout in it's arrangement and it's a high performance car with front wheel drive to boot and I have not heard of any trouble with those. Just my opinion and I am sure others, including dealers are reusing those bolts. But, it WILL make you feel safer to replace them, understandably.
Charles