Not commenting on topics is fine (and arguably even the default) response.
Don’t allow yourself to feel (or be) obligated to answers questions about a past employee, portfolio company, or similar. If you choose to you can, but the answerer chooses, not the questioner.
But he made an initial decision to not comment only to now comment after several months of rumors, so there was clearly a recent change in PG's thinking on the right way to handle this. That raises the question of "what caused that change?"
Don’t allow yourself to feel (or be) obligated to answers questions about a past employee, portfolio company, or similar. If you choose to you can, but the answerer chooses, not the questioner.