Thus there is nothing wrong with the creator obtaining some exponentially diminishing seigniorage. And PoW's great contribution is in the objectively, competitive distribution which runs on auto-pilot and doesn't require ongoing seigniorage (except as pointed out above the seniorage of the government utilities it furthers and also the fact that economies-of-scale centralize it and create an ongoing seigniorage, which is really, really bad and why Bitcoin is in a scalepocalypse political clusterfuck as the power vacuum must be filled). But PoW doesn't actually destroy the value transferred in the process.
There are two remarks on this. First of all, holding a seigniorage-obtained fraction of a collectible which grows in market cap over time, gives you a proportional growth in seigniorage, without doing anything. If you possess 5% of bitcoin when its market cap is 1 million dollars because of seigniorage, and bitcoin goes to 1000 billion, your seigniorage has grown proportionally. So you DO gain continuous seigniorage by just holding the coins. That is even the case if you wasted 50 000 dollars to obtain them, that is, if you destroyed entirely the initial seigniorage when you created them. This is the problem with a "sound money" collectible as a monetary asset. You could formulate it that its seigniorage properties are not invariant over time. This is a problem in my opinion.
The HODLer has an opportunity cost which is not free. The external economy didn't just cease to exist while he was HODLing.
Sitting still in your chair is not free and has a (n opportunity) cost.
It is not because I bought something for 10 000 dollars with bitcoin, that the bitcoin system created me an economic value of 10 000 dollars, it only transported it (like the truck) ; as such, it did bring me some small value because otherwise I would have done it with fiat, but this is a very small amount.
However, the holder of "seigniorage bitcoins" takes the full value that is transported as reward, and not just the value creation by the bitcoin monetary system. This unfair economic advantage makes that one hugely overinvests in this system. In other words, the seigniorage-by-holding-coins is a huge market failure, that directs tons and tons of resources towards something that has very little economic consumer value.
This is not quite right or not the complete story. Society needs both savings and consumption. The money supply can growth faster than GDP, but any way the Quantity Theory of Money is not accurate because the value of money is complex and intertwined with confidence and derivatives.
It is quite complex, because even for example we may need that effect you lament to counteract the extreme level of money supply growth in the early distribution phase and also to encourage early adopters to invest in the ecosystem and not just dump their tokens for fiat (for the more liquid unit-of-account and unit-of-exchange).