Samoyed weren't originally made for sledding but adapted well to it. FWIW a lot of competitive dogsledders have foxhound blood in their personal lines because the crossing gives them a synergistic effect on endurance. other have pit blood crossed in for more heart. and i beleive someone here posted a link to a person who regularly runs & finishes the iditarod w/ a team of standard poodles. the point being dogs are very adaptable.
i think by "true sleddogs" they meant what the breed was originally created for not adapted to later. keep in mind it's been well over a century since the russians introduced the samoyedic peoples to dog sledding and since then performance in this area has almost certainly become a factor in breeding decisions, but maybe not the deciding factor. for malamutes other NA native northern breeds sled work has ALWAYS been the driving factor in breeding decisions.