"Store of value" here means "investment", but people are trying to keep the veneer of currency definition. And of course it's a highly speculative investment, although whose wild volatility contains a rare spice cherished by asset managers, "high alpha", meaning that it is not related to the broader markets. In musical terms, Bitcoin sings its own song, or dances to its own beat.
To diversify, as modern portfolio theory prescribes, investors seek assets whose prices don't change in relation to other prices, are uncorrelated. In today's world, most markets are highly correlated with each other, they are almost like separate instruments playing in a huge symphony.
But not Bitcoin. Not for now. Bitcoin moves according to bitcoin.
If bitcoin becomes more and more like "digital gold" and loses some of the volatility, however, it will also start to act more and more like physical gold on the world markets. Gold moves as a safe haven asset, and so will Bitcoin, and thereby lose its status as an investment uncorrelated to the broader markets.
If you're involved in trading, you can pretty much be given a single market quote like the S&P or gold, and generally guess the direction and possibly the amount of price changes in many or most other world markets, unless there were events specific to one or another market. Usually if gold went up, for example, the Japanese yen also gained. These relationships change over time, but they are very pronounced. You can ask maybe three questions and generally extrapolate what happened over the entire world except for cases where a local event in India caused its bourse to move independently, or for example a weather event moved an agricultural commodity. Even real estate does not escape the bonds of market correlation.
But... Bitcoin. Without a very large move in other assets, I doubt a well-versed market participant could tell you what happened to Bitcoin without hearing about Bitcoin itself (or maybe Ethereum...). To repeat myself, I believe this will change if BTC becomes established as a "store of value", it will join the symphony, but for that reason it will also lose its great appeal to institutional investors -- its uncorrelated quality, "pure alpha" as one well-known asset manager recently termed it (where alpha is independent returns and beta is benchmarked correlated returns).
So, with its volatility, Bitcoin is maybe being thought of by institutional investors as a kind of extreme spice that can add a bit of diversified risk into their larger stew. Just dab will do ya. But as more dabs are added, the "alpha" quality will wear off and it will begin to move more and more like plain old gold. Maybe less lustrous...
So maybe in investment terms as well, Bitcoin might have a scaling problem.