Why would he say they're all dead, if they really aren't, but, actually Time Locked instead? Why would he say he destroyed them all or killed them all, when he really didn't?
For all intents and purpose, they're dead. They're gone, they can't be reached, the Doctor will never see them, they're caught in a loop and will never do anything productive ever again.
Whether you like it or not, the writers' clear intent is that the Doctor is the last of his kind, not that there are lots of Time Lords out there and that only those who were on Gallifrey during the Time War vanished. Otherwise the whole thing has no dramatic weight.