that's entirely possible but out of the 6-8 people I know with 08s who have aftermarket springs on factory struts, none of them have had a problem... I've only seen it on this forum with people who installed them all wrong
here is no really wrong way to install struts, i do admit that the vice grips might not have been the best idea , but where i used the vice grips there was no way that they could get near the seal to damage it. either way i am getting new ones for free. There have been quite a few people that installed them right or had them installed and they still have destroyed the stock struts. Subaru has admitted and my dealer also told me they know the 08 struts are crap.
1- using vice grips on any sort of shock is not the correct way to do it... it might "work" but it's still wrong (sort of like jamming a screwdriver in an oil filter to remove it). the 100% correct way to do it (and the way subaru service technicians are trained to do it) is listed here: http://www.driveperformance.subaru.com/version5_2/feature.asp
2- subaru hasn't admitted anything officially... some rep might have told you that to be nice but there's no TSB on the 08 shocks
3- dealers (service writers that is) notoriously don't know what they're talking about, see #2 above
I'm glad... subaru replaced my pressure valve thing in my gas tank for free when it had a spider web in it... the dealer charged me $300 to poke a screwdriver in there... it was broken the day I bought it though, and the SOA rep said he had heard of 3 other people have the same problem... so SOA took care of it... no TSB on it so it's not an official problem.
this is just one of those things we run into with a new design