Board Thread:Character Discussion/@comment-25205238-20190821213710/@comment-36180144-20190825215227

Russell could have meant he had hope (which were extinguished by Clarke) for man's best friend's fate.... on Earth. Which would mean nothing about their presence, population, or prospects in Sanctum.

Just because we don't see any others on Alpha, doesn't mean that no others exist there.

At least that's how I read it. Nothing definitive.