My go-to for the perfect issuance schedule (in a vacuum, if I were to reinvent Bitcoin) has always been a constant number of units every block until recently when I'm not even sure about that. But constant issuance does not at all increase the supply steady with the expansion of productivity. It increases the supply in step with how well people avoid losing coins until people are losing that many coins per block again on average, and it therefore tends to only replace lost coins on average. Still a very very hard money. The quantity of money remains fixed with tail emissions, given a certain set of practices for coin loss mitigation. As soon as those practices improve, some slow increase in the money supply happens and this causes less deflation, which incentivizes people to be more loose with their money and spend or invest a little less carefully, or use alternative monies without tail emissions or alternative investments.

In short, a money with tail emissions does not increase with the growth of the economy.