You’re correct that slop in the threads just means some extra backlash. I could see, depending on the construction of the vise, having some axial play due to that slop being bad, but vises usually have some other means to control movement in that direction. The only thing the threaded piece does is push or pull.
https://www.westada.org/
As close as I could get. I couldn’t find in a brief search of the site if there was a staff lookup. But I’m pretty sure you can look up an licensed teacher if you know what state they’re in, which Is how I found that she’s licensed and active in that district.