I'm glad you mentioned this. Indeed, there are two different things. First is the linearity of blocks and the second is the linearity of the emission of units with which we transact. Bitcoin has the former, but does not have the latter. You can't unambiguously say "I'm going to buy an hour of Bitcoin" because this hour depends on _when_ you plan on buying them - the emission over any time interval (including one hour) changes over time due to the halvings. This is why I think coins with a constant emission (especially Grin where 1 coin is emitted every second) can bring to life the saying "time is money" because money becomes time. There is no difference between calling your 100 Grins "100 Seconds" and buying an hour of Grin. So yes, you're correct that the article talks about the "block time", but I think this can be pushed further where you not only have a global clock for events, but your unit of money is time itself.

P.S. I prefer thinking of a blockchain as a "drunk" clock, because of the variance that comes with the finding of a valid PoW. It might sway a bit left and right, but it mostly goes in the straight line in the end.