Finally something new and worth to read. I'm not familiar with this "stock to flow" in Finance. Let's see what this is about:

Oh, it's basically a measure of scarcity, by looking at the "world inventory" and the amount produced annually.
https://monetary-metals.com/gold-economics/lexicon/?mmdesc=stock-to-flow-ratio#stock-to-flow-ratio

This model should suffice for an academics paper (at least in my country). However, it might not get an accurate result for forecasting. It still utilizes historical data, right?
For forecasting purposes, however, this model can be used as one out of many models and assumptions.

The good news is, as Satoshi said, if you can get enough people to believe this model, it will be a self-fulfilling prophecy.