I dunno, mage, but it looks like if this was a serious issue, it would have been all over the interwebs for the last 9 years.
This is the first I've heard of it.
Admittedly, the seller states that he doesn't "have a clue" as to the veracity of the "amp geek's" statement. Seller also states that the amp has had a lot of work done to it. If pre-2001 amps are so much more reliable, then why has it been in the shop so much?
All of this adds up to me to be an ad for a cranky amp that the seller has put in a lot of money to keep running, and he's trying to unload it, getting as much of his money out of it as he can.
Amp builders may have been forced to use different solder, I don't know. But, if it was a problem, you'd be seeing A LOT more complaints.
I think it's a load of fecal material.
Guitars:
Fender 2006 MIM Fender Stratocaster HSS in 3TS
Ibanez RG 570 with a bridge Invader
ESP M II Deluxe with a Tune-o-Matic bridge
Eleanor, the magical, mystical Road Worn wonder Tele
Blackstar HT Club 40