Ok re-read my statement, "usually, not always set in stone but a good starting point". I ran clay compound switches on a hard pack blue groove this weekend. It was the best tire I ran out of four qualifiers, 2 of which I ran M3 Holeshots or Soft Compound Switches. At buggy nats I ran Soft Gators on hard packed blue groove and they were the best of the weekend. BTW, I'm referring to 1/8th and Arena Truck. I've probably got over $2K invested in rubber just for my scale.
I'll also add that at the buggy nats in the A Main, Gosch was running M2 Bowtie's on hard packed blue groove and I think Drake was on XTR Bowtie's.