Jumping here in the middle.
I'm wondering if the "Sustain Shield" is nothing more than slow-dissolving Cal-Hypo. After all, the "special" stuff was 62 or 68% cal-hypo...which is the NORMAL percentage of Cal-Hypo.

If so, then it has obviously NO effect on CYA.

The B-B-B system is really replacing the $$$ and guessing with knowledge of what stuff does and when to use it.
B: Bleach, B: Borax, B: Baking Soda, plus, of course, CYA and Muriatic Acid are basically all you usually need.
BUT

At the beginning of the season, when my CYA levels are low and my pH may be higher than I like, I like to use Tri-Chlor tabs to start because they add acid and CYA while maintaining chlorine. If the CYA is low but the pH isn't high, I may well use Di-chlor powder...because it doesn't lower pH much but adds even more CYA than Tri-Chlor, and I think faster than CYA powder.

I rarely use Cal-Hypo. It's getting harder and harder to find 68%--it's all that 48% garbage. I don't need calcium in my vinyl pool, so...unless I cannot get bleach or LC (my preference) I don't buy it. But I did in the past and used up what I had.
The two most important measures in your pool care are chlorine and pH levels.

CYA is third because it determines what the optimum chlorine level is. T/A is useful if your pH is unstable because adjusting T/A can stabilize it. And, unless you have a concrete-tile-type pool, Calcium is only important if it's too high, high enough to cause problems.

Finally, sometimes people have metal problems but those have very distinctive symptoms and even then, the solution is straight-forward.

What's my point? B-B-B is a KNOWLEDGE system that makes pool care super-easy and obvious and removes the mystery--and expense.

Pool Forum was the first to advocate for B-B-B and it has been picked up by TFP and other swimming pool sites. B-B-B (or "BBB" as most put it ) is a nice convenient shorthand for the key elements of what makes it all work.

No mystery!