Bitcoin stock to flow model is wrong because:
The basis of the entire model assumes that halvings create exponential price increases because miners lose half of their ability to depress price. Bitcoin inflation year over year inflation rate is ALREADY less than 2%, so whether that rate is 1%, 0.5%, or 0.25%, miners have no tangible effect on price because it's already practically zero. The stock to flow ratio might matter when only 4,000,000/21,000,000 were mined, but with 19,000,000/21,000,000 mined, the introduction of those last two million coins over the span of a hundred years will mean nothing going forward. For all intents and purposes, you are better off assuming bitcoin is already at 21 million and that there are no more coins left to mine.
Bitcoin might follow the stock to flow model anyway for the next few years, because one word: demand
The volatility index of bitcoin has been sitting at all time lows for the last year but the price is trending slightly up, usually that's indicative of an asset that is consolidating for a massive breakout. Think of bitcoin in 2016 as a good comparison. Of course bitcoin does not have a tangible intrinsic value per se, but it has an intangible value and that is: trust. Despite being in a nasty multiyear bear market, the on chain metrics for bitcoin have been pointing north the whole time. The people who believe in the fundamentals, the ones who believe in bitcoin are the ones keeping it alive and it's still growing in the background. The global economic circumstances with unlimited quantitative easing are favoring hard assets, and bitcoin is about as hard as it gets. Smart money aka institutions and hedge funds are buying bitcoin right now. Usually the entrance of smart money is a sign further appreciation is coming.
This might be bitcoin's last exponential bullrun. At some point, market capitalization gets so high that it just can't mathematically appreciate exponentially anymore. At 200 billion, the marketcap is already pressing on those limits, but with the increased demand I'm forecasting is coming, I think bitcoin will have one last hurrah to levels in the multi-trillions. Unless Zimbabwe style hyperinflation is coming, bitcoin will find a ceiling that it will never touch again and peak.