I think his point was that the market of gold or silver accepting businesses are roughly equivalent (close to 0) but the same cannot be said for BTC and Alt Coins and so the comparison breaks down to a certain degree.
The comparison never held to any degree anyway.
There is physical/practical limitation to the divisibility of gold for day to day transaction.
Same thing with silver, which is why we also had nickel coins, copper coins, etc.
You can divide a cryptocurrency as much as you want.
Really, the comparison should have been crypto-b is like the Australian dollar to the crypto-a Canadian dollar.