Sure, any clay will scratch if you dropped it....
Never heard that one regarding Clay Magic.
David has some fine clay on his "SHOP" site which you should look into.
Bottom line, wear latex gloves when using clay to avoid pulling dirt/oils from your hand. Use a good lube and always clay wet!
Fold clay often and inspect it during use to see or feel any larger particles that pulled off on the clay. If so, grab another fresh one and continue. Clay is cheap, polishing a finish because of marks is no fun!
Just take your time, inspect often, etc.
Regards,
Deanski