The Blockchain is the slowest and at the same time most energy hungry Datastore mankind has ever build. And in the case of bitcoin it's not fit for the job it was developed for.
There's no way for the blockchain to validate time stamping due to fluctuation in hash power and the nature of an adversarial network with untrusted data.
What's been happening is blocktimes wildly fluctuate, anywhere from 20 seconds - 90 minutes + even though the software attempts to calibrate for 10 minutes.
He just means things are unequivoqually ordered in time, so each block is a time stamp. Not necessarily running at constant frequency as our other time keeping tools.