I think their way of comparing different proof-of-work algorithms was to calculate the energy consumed in each chain to provide the current hash rate, which is good, but the number will be useless if the blockchain has a low hash rate, as no matter how many confirmations there are, your transaction will not be secure.
But the time calculation is not accurate. For example, in the case of Bitcoin, you need to wait for a period that may be relatively long to get one confirmation and then wait for an hour to get 6 confirmations, while in altcoin your transaction is confirmed directly. Therefore, in terms of time, Bitcoin may not be the best, but it is the safest.