Now you see why nobody at TFP puts any stock in pool store tests

...I'm assuming you went for the metals testing, but as you see, even those don't accord

Right now you don't need anything they said so ignore.
But your
SLAM Process isn't over until you meet all three criteria (including crystal clarity) and pass the
Overnight Chlorine Loss Test and you must finish the slam before addressing the stains or adding metal sequestrants because to do otherwise would possibly wreck both treatments

Slam value FC breaks down metal sequestrant.
So when you're finished the slam, post a picture and your own test results and we can try to figure out the staining.
To get ready for a stain treatment with such inconclusive results, it may be worth orderng a Jacks Magic stain test ID kit and then following their protocol based on the results. You'd be able to see whether your staining is more iron or copper in comparison.
If you go with the Jacks line, the Jacks Magic Pink is the more aggressive sequestrant for metals. Whether you do an AA treatment or a Jacks treatment or acid wash to remove stains you will need sequestrant to apply after the treatment so you can get that now.
The reason I'm suggesting the Jacks stain ID kit isn't because I've bought stock in the company or anything...its just that I don't want to see you go to the time and expense of an AA treatment and not have it work effectively.
If you prefer DIY testing, you could get some dry acid and do the vitamin c test against a dry acid test on the same stain area. If dry acid works better in the same time, ten its more likely copper.
With iron, the vit c should remove the spot it sits on completely.