Wouldn't have been a Nationals (one would hope!}, as strict adherence to the published National Rules is mandated.

At other range-day shoots, anything goes within reason.

I can't see any sense in using the back trigger first if a quick follow-up shot might be required. That would negate the instinctive use of the double trigger developed over time, and lead to a f*ckup sooner or later, with possible casualties in the hunting field.

Using the back trigger when only a single shot is required however, such as a finisher, would help even-out barrel wear to some degree.