Should be easy to obfuscate if true - use gloves, use dirt/grit on the screen, use oily fingers. Edit:why disagree? I bet you could even create textured screen

Should be easy to obfuscate if true - use gloves, use dirt/grit on the screen, use oily fingers. Edit:why disagree? I bet you could even create textured screen protectors with randomized patterns to obfuscate they swipe.