I think he's been using the drugs he's been selling.
C$4200 for a '91B4 w/44K Km's?
Even the starting bid of C$2500 seems on the high end!
ANY 2-stroke? That's an awfully big category. It would include the >175mph TZ750, too. (He didn't say street-legal.) It also doesn't take a lot of tweaking to make a fast RZ350 (he didn't say stock, either). I'm pretty sure the old Kawi & Zook 750 triples would outrun it, too.
Heck, I had my '75 RD350 over 110 mph... and it had no trouble dusting SOHC 750 Hondas of the day in the 1/4... even the stock 1G DOHC ones.
(It wasn't exactly stock though)