Load testing would have to be quite advanced to find this, doing more than just simulating users for the most common features. It took more than 24 hours of real-world usage to visit sufficiently many niche code paths to fill the code cache.
ITT: People missing the point by making it about software licenses, when the real issue is lying about the product.
ChessBase could easily comply with any open source license by linking the full source code, including the method they used to generate NN weights (if they think the license applies here as well), in a footnote.
It would still be a scam, because their claims of superiority, originality ("almost from scratch"), and innovation (see the funny part about technology from Japan) are wrong, and purposely so.