If anyone is using magnet cleaners on low-iron glass, you should expect the glass to get scratched. In fact, using them on regular glass will probably scratch as well.
Low-iron glass is softer than regular glass, so you have to be careful with it. It has nothing to do with the quality of the glass. I've had the same tank for 8 years and I always carefully scraped the glass by hand until about 18 months ago when I got sick of putting my arm in the tank 2x a week. I bought a Flipper, which I never leave in the tank, always carefully clean afterwards, and only use the blade side. Within a few months there were tons of scratches. They aren't a big deal except at certain angles. For 6 years of hand cleaning, I never had a single scratch.