Cold War submarine speed changed the anti-submarine problem without removing the convoy escort's purpose. An attacking submarine still had to find and approach the convoy, bringing it toward the defending ships. Escorts therefore did not necessarily need to match the submarine's maximum speed in an open-ocean chase. Their position around the target let them organize the interception on more favourable terms.
Notable Point · 8:43-9:05
Fast submarines still had to find the convoy
Very fast submarines did not make convoy escorts pointless because the attacker still had to approach the formation those escorts protected.