This article is an opinion piece.  There is nothing in it that constitutes proof.  So you should refrain from using the term "proves you wrong" as it does not.  The basis of the article is to take some past behavior and project it into the future.   This is what is known as extrapolation.  Proof by extrapolation is not really a thing.  Also, in finance extrapolation is known to be a poor tool for anticipating the future.  For example, look at XRP, it's grown 50x in 2 months.  Let's extrapolate that to the end of the year.  Oh wait, now XRP is worth 50^3 = 125000x its current value or >100tt usd market cap. Now I've proved that XRP will be worth as much as all the worlds equities by the end of the year.  It must be true, because I proved it (would it help if I provide nice charts to show this proof on? I can, so please don't doubt its veracity.)  The proof that you offered about BTC 2019 volatility is worth just as much as the one I've offered about XRP end of year market cap.

The irony here (situational) is that while you accused one person of blindly accepting formulas (he didn't, *), you have blindly accepted the analysis of a blogger and stated it to be fact.  Are you able to see the irony in this?

(*) It's helpful to understand that V is simply defined to be the variable which makes the formula true.  So by definition the formula is always true.  It's sort of like blindly accepting 1=1.  If you can accept that, then you should be comfortable with Fischer's formula.