>Bitcoin was less volatile than AMZN or AAPL in 2020 (3-month realised volatility)
Not sure what you are smoking. Bitcoin literally just went between about 27k and 34k today. That's about a 20% swing.
Ethereum had a 60% swing.
Not volatile at all! Nope, nope, nope not at all.
But even on daily %-change in 2020, BTC doesn't look different to other stocks: https://imgur.com/a/mE7bSI4 (the green one is TSLA by the way).
Since we are talking about a company putting $400M of BTC in their balance sheets, I doubt they are worried by daily volatility.
Now you are retreating to stocks for a comparison. Indeed, if Bitcoin is supposed to be treated like individual stock, volatility of Bitcoin becomes reasonable, but it is still very high. That is why you do not put all your money into a single stock. You diversify, like in an index fund. Compared to an index fund, Bitcoin volatility is ridiculous.
Unlike with stock, there is no index fund for cryptocurrency that is substantially less volatile than Bitcoin itself.