Ya, ive never had anything even close to that happen with coin snap. I know it gives the option to edit the details of a coin etc on the page when you're adding it into the collection database. And it'll read whatever you want when you're on one page with your coin and stuff, but it does tell you if you decide to change any of the details it may affect the recommendation value they give it which really only is seen or realized on the summary page with your collection as a whole, not on the one coin you're recently on and going over...
To be honest if anything I thought it was gjving some coins a lesser grade than they deserved but maybe it was picking up scratches or wear my eyes couldnt see which is very possible since my eyesight has gotten pretty bad over the 38 years of my life... All I know is coinsnap has never done anything even CLOSE to what that guy said and warned about in my experience, so I encourage everyone to try it out for themselves and don't just take his or my word for it but be your own judges. Try it and then decide what you think about ita accuracy and usefulness. Just wanted to point that out since I recently just got that app actually and started using it about 3 days ago and I LOVE it. I was SO impressed with how remarkably accurate and impressive I thought it was. Just my opinion.