That's not what the paper says though:

    Claude Opus 4.6 Anthropic 68.0% ∼5.3T [1.8–15.6T]
    Claude Opus 4.7 Anthropic 66.4% ∼4.0T [1.4–12.0T]
    Claude Opus 4.5 Anthropic 65.2% ∼3.4T [1.1–10.0T]
    Claude Opus 4.1 Anthropic 64.9% ∼3.2T [1.1–9.5T]
    Claude Opus 4 Anthropic 59.7% ∼1.4T [478B–4.2T

According to their estimation, Opus is likely between 1T and 15T, which really doesn't tell you much that you couldn't have guessed otherwise. It doesn't say “Opus is a 5T model”.

The fact that there's absolutely no consistency in the predicted size between models from the same lab should tell you all you need about the predictive power of this method (and they aren't really lying about their numbers, their confidence interval is huge enough to fit anything in it, but their prose is making very strong claims out of their statistical nothingburger).

(somebody already posted this paper earlier, and I spent some time reading it, and this paper is really not that good even though there are a bunch of interesting ideas in it).