We use Gaussian processes trained on vetted test data from academic and industry partners. We use these predictions to recommend mixes for onsite testing to accelerate finding mixtures with optimal strength-speed-sustainability trade-offs. None of the data and predictions go untested. The blog post goes into this in more detail.

AI isn’t just LLMs.

Can you at least read the article before criticizing them? They explicitly call out that they use Bayesian Optimization (Gaussian process) thing for this. It is "AI" but not "LLM" like you think it is.