How Oscar-class submarines fit a carrier-killing attack

Why are Oscar-class submarines considered SSGNs rather than ordinary attack submarines with missiles?

Their primary mission is a coordinated anti-carrier missile ambush, with torpedoes secondary to the large dedicated missile battery.

The Oscar class carries torpedoes, but its defining job is to approach within missile range without being detected. It then launches anti-ship missiles as part of a multi-axis attack. Backfire or Blackjack bombers could attack from another direction while a Kirov or Kiev group added a third missile stream. The doctrine aims to saturate carrier defences through coordination rather than rely on a submarine torpedo duel.