I was just watching this video and couldn't understand what Greg Davis meant by his comment at the 5:00 minute mark as he discusses backset and sourmashing.

Sourmashing is required in the definition of bourbon? Did I understand that right?
What of the Woodford Sweet Mash bourbon experiment?

I'm not trying to do a "gotcha" of the bourbon pro, he must have had something in his mind.

It was probably a slip between describing common practice and stating what's a requirement, like how many people mistakenly believe that since all the bourbon they know of is made in Kentucky that bourbon is only allowed to be made in Kentucky. Interestingly, if US regulations had wording similar to the Canadian Whisky wording (which I believe has a clause that reads something like "must have a character identifiable as Canadian Whisky) then at a certain point common practice indeed does become part of the regulation.

This makes me wonder whether microdistillers commonly use a sour or sweet mash. I would venture that sweetmashing may be practiced by some microdistillers, but since the industry is still in such a growth and exploration phase any number of things are subject to experimentation.

Does anyone know distillers who sweet mash bourbons or straight American ryes?