Again, a "constant upward trajectory" creates zero volatility.
Reading comprehension.
I was never talking about "constant upward trajectory", but about "constant upward trajectory with volatility around the trajectory"; or in other words random deviations from the trajectory.
Is the trajectory constant or not? You are employing a loose definition of the word "constant" to make your case here. Within the "random deviations from the trajectory" could exist several other trajectories, depending on what span of time we're talking about. Within the cluster of those sub-trajectories exists risk if you are a shorter-term trader.
You didn't even know the trajectory was upward until after it had taken place, so to say it was a "risk free" investment is a statement made
after the fact, and basically meaningless. Its like making a prediction on 2015's price of bitcoin in 2020. Sure, after the fact, we can say that the overall trajectory was up, and there existed a lot of volatility in the middle. But nobody knew it was a risk-free investment in 2015.
Volatility, in essence, is nothing but a random oscillation around a potentially unknown trajectory.
This, again, means that you can have assets of arbitrary volatility that fall into all three categories of: 1.) negative risk 2.) positive risk and 3.) neutral risk.
This all has to do with the span and timing of your trades/investments. Stocks and other assets go up and down and many have several different trajectories within their lifespans.
Bitcoin is just one of a countless number of assets and has no relevance to the definition of volatility.
It may serve as an example for an asset with high volatility and negative risk (e.g. an expected long-term return greater zero) that may, despite having a positive expected return, still reduce your capital to ashes; which makes it a rather interesting case.
It makes it risky is what it makes it. Who gets to decide bitcoin has a "positive expected return"? And for what period of time?
But that does not imply that all volatile assets are risky.
Everything that is traded under the sun has a certain degree of volatility and a certain degree of risk. The more volatile something is, the greater chance exists for financial ruin. It seems to be a no-brainer. Don't know why you would argue against that.
Arguing about hypothetical situations taken advantage of to the maximum degree doesn't negate the correlation between risk and volatility. You should probably give this a read through:
https://www.investopedia.com/terms/v/volatility.asp