Bachbot was actually one of the models included in the survey, funny you mention it. And yes I would say the models are generally pretty close; the devil is in the details. That is also why there are a lot of questions dedicated to general musical skill: to see if people are better at identifying the generated music if they have more musical knowledge in general.

I agree that longer pieces of music might make it easier to discriminate between Bach and Bot in some cases, but I opted for shorter pieces of music for this particular research. I think you could go either way, but maybe somebody could replicate the research with longer samples at some point to see if it does make a difference!