Todd Howard was technically right about the 'no one ever enters/leaves Vault 101'. It was explained in the game that it was a lie set up shortly after Wanderer and his/her father entered the Vault.
As for the 200 years thing conflicting with 'New Vegas' and the 'No going back in time' rule. Well, remember, Obsidian made New Vegas. They decided to bump the date to 2281. The last Fallout game that BETHESDA made was Fallout 3, which started on August 2277. So technically Bethesda isn't even breaking their 'no going back in time' rule if they bump it up to just a few months later.