You’re referring to the GP cover story from 1980, right as WACF was released.
I recall he said they used to tune down to C# as creating Mike’s troubles.
Or he might have said D-Flat.
But considering most of the Dave-era was something close to E-flat, I don’t think your recall is entirely accurate.
At the risk of being pedantic (aw who am I kidding? This is TGP ) I was sitting in the car wash waiting room and found the quote.