Everyone and his dog are free to have their opinion
But that alone doesn't translate into profit "optimization on an aggregated level" (I don't really know what you mean by this). Nevertheless, holding your coins cannot possibly be an optimal strategy since the only case when it becomes such never happens in real life. That strategy would be best if Bitcoin (or any other such asset, for the record) was going up in a straight line. But this is never the case. So selling a fraction of your coins and buying them back is a more profitable strategy simply statistically. You may not always hit it 20/20, but in the long run you would be better off than just sticking to your coins (even if there were no major crashes)
Aggregated level:
The sum of the individual profits of the group who choose for a selling-strategy. The profits of individuals will have some kind of distibution
That would be like an average body temperature across the hospital (mortuary included)
You simply can't compare that to a one-size-fits-all holding strategy, i.e. a strategy where all members of the group just hold to their bitcoins. If you still want to compare these strategies, you obviously should compare a group of individuals sticking to the same BTFD strategy. But that would be equal to comparing just one individual following his variety of that strategy to another individual who has married his coins. Moreover, you simply can't use your "aggregated level" since profits just like losses are an individual, not a group phenomenon (especially in a zero-sum game like Bitcoin trading)
Talking about hospital: I’don’t like the perspective being part of a test group who is swallowing the placebo. Maybe my search for an econometric principle is to simple.
Zero sum game: how do you define the playing field? On a certain scale, isn’t everything a zero-sum game?
I don't know about a certain level but ultimately not everything is a zero-sum game
Basically, we use free resources which were given to us by the Universe or God if you please (e.g. energy, air, water, etc), so for us, humans, it is certainly not a zero sum game. Even in respect to markets, the zero-sum game approach is applicable only to financial markets (Bitcoin belongs here as well), but if we talk about, say, commodity markets, this is no longer the case. For example, a buyer purchases a barrel of crude oil from which he makes a few gallons of gasoline that he sells to his consumers, so it is a win-win situation for everyone, starting from an oil extracting company to a consumer who is driving his car fueled by what has once been crude oil. In other words, crude oil here is conceptually a free lunch which is shared between a few interested people
What I learned from the basics of physics is that we don’t create, we only transform. Only the transformation can be irreversible. On human level it’s not zero-sum, on (sub)atomic level: it is.
Going to the markets: Keynesians, Friedman and followers consider a relationship between the monetairy (financial markets is a subset) and commodity markets, money supply and intrest rate determine price level, and supply and demand in commodities. They are interrelated, so if there is no zero-sum game in commodities, there is no zero-sum game in monetairy (incl. financial) markets (including Bitcoin, I like your inclusion of Bitcoin). However, the sum of commodities and financials/monetairy may be zero.