There is a big difference between dumping a dataset in the latest hot ML model and building something that offer some actual explainability, deal with intrinsic biases, have some stability over time and recalibration and that will go trough an unprecedented crisis for which you don't have any data to learn from. That mean the model usually has to go trough a lot of internal commities and different external agencies. I highly suspect that an external proprietary solution won't go very far in the credit rating field.