Ah, excellent response - thank you.
So it was Jeff Cooper who said this. Jeff is a SAO master, making his training and work in the field 1911-centric.
While not staying exclusive to the 1911 his ideas on carry status are tailored for that gun (Beavertail safety, hammer back in carry)
The method doesn’t jive well for the Sig or Browning SA/DA designs.
Like taking advice from Ayoob. His advice is sound, he is a world-reknowned pro. But his attention is on the revolver. Doesn’t make him a fool with the semi, but most of this train of thought is based on the revolver.
These modes work with my Browning hi-power, which of course is SA.
Jeff was a fan of the CZ 75, which is DA/SA, though he was not a fan of 9mm. He helped with the Bren 10, which is a CZ derivative in 10mm. The CZ 75 can be carried decocked (DA first shot) or cocked and locked (SA).
https://en.wikipedia.org/wiki/Bren_Ten