As you may know, acid staining is a reactive process, creating a translucent color that is actually part of the concrete, not a coating on top. That is both its greatest strength and weakness.
It’s good in the sense that it can’t be just scraped off, to get rid of the acid stain you have to physically damage the surface of the concrete, it won’t just peel off or fade away. At the same time, since it’s a reactive process, anything that interferes with it during the application will create unusual results, which was very much a possibility in this case.