Sure - but I'm just talking about the disparity between his claimed r2 value (for which he does not actually provide the calculation) and the output of his own model. It's totally fine to say that the correlation between the two values is exponential instead of linear, but it's not logical at all to say "My model is super accurate, r2 = 0.95, but the output I'm getting from the model is wildly inaccurate when actually compared to all recent (including current) price values (error of ~100%)."
He used his model to derive the $18k value, himself, so it clearly must factor in the 8.7 exponent you're referencing. It still resulted in a massive error when actual data is compared to the best fit model. What's worse is he goes on to imply that either BTC will increase or S&P will decrease simply because current values don't fit his model!