Why does protected mode disable pinch zooming with the trackpad?

I noticed recently that I couldn't pinch zoom PDF documents with the computer trackpad in Acrobat Reader DC anymore, and learnt that disabling the "run in protected mode at startup" in the "Sandbox Protections" section of the "enhanced security" options enables pinch zooming again. I find this very strange and don't understand how enabling or disabling pinch zooming has anything to to with security protection. Can someone enlighten me?