Steve:
Like Henry, I've never seen a pulled stud on an aluminum-cased engine unless they were improperly installed. In the case of high HP Turbocharged race motors like 935's, other things happen first such as head lifting.
The only issues I've seen to date with ARP are the occasional loose head nuts but not a pulled stud. Either they were improperly installed or this is the first instance of pulled studs from expansion-related stresses.
I'm not one to speculate but it seems that if this was due to stresses, several of these would have pulled their threads out,......OTOH, the combination of too much torque and maybe a loose one might have been the culprit. At this juncture, any accurate forensics will be almost impossible to do.
If it were my engine, I would sell those ARP ones and install the 993TT Dilavars.