Yeah, I've never been a fan of this stuff. The version we carried was Spaguard (Bioguard).
I was 16 and at their annual Chem School when I raised my hand in the auditorium and asked: "Since this stuff purges calcium from the water AND holds your pH stable, is there any reason to use Stain and Scale control as a maintenance chemical (adding S&S was at the bottom of EVERY water test printout)?" The guy giving the presentation said "No, you don't need to worry about that."
Then someone else in the audience raises his hand and says "But it's still on the printout!" So the guy teaching the class says, "Oh, well if the computer says you need it..." Nevermind any chemical reasons or that metal staining could still be an issue. It's on the printout.