I'd like to request consideration for migration back to ELU for this question:
To address some of the noted concerns:
No precise definition of "correct" exists. | This concern is overcome because results are measured against a "gold standard", and for any penalty the system creators are given the chance to flag a correction as a correct alternative which is manually reviewed by the judges.
Other ELU meta discussion by senior members seem to support such a question. The idea of questions about grammar, syntax, correctness, even if such questions are of interest to linguists or serious language enthusiasts.
This is not a request for resources and the question is not subjective. It can definitely be answered precisely. In the time since posting I have discovered an answer and would be glad to add it.
Thank you for taking a look -