[parallel_item]

I think a key factor in this decision may be the perceived risk of putting huge capital behind a single black box model. I would assume this differs from more ML-heavy quant firms like Two-Sigma, because BlackRock's products generally perform at a huge scale with some central idea behind them. Two-Sigma probably can spread out the same amount of assets across many different black-box models, diversifying and reducing risk through these means. In this case, perhaps only 1 model dictating such a huge chunk of capital was just too much uncertainty?

I have no evidence of the scale and diversification of both these, so evidence would be helpful in refuting the above!

[beta_binomial]

I think so. The ultimate question is who are you going to sue and who is going to sue you if something goes wrong? Imagine having to put your ML researcher on the stand and having him say "I can't say for sure that this or that didn't affect the outcome in a meaningful way"