The Mystery

Or near impossible to get them right.

It seems like some incarnations of the Doctor simply do not exist... Or the ai adds Companions that didn't exit in the previous episodes... Like here. The woman looks a lot like Donna Noble if you ask me, but I suppose it must be Sarah-Jane Smith.

I think this maybe because there's less data to train the I on these older incanations, or simple less interest as they seem less popular.