How to hide or spoof bootloader info from any app?
Install XprivacyLua and select use tracking Pics below show the difference in output




For spoofing instead of hiding you may have to use custom hooks. You can ask on the XDA thread of the app or use the pro version of the module to change values globally or on per app basis



Caveat

Quoting Namnodorel from comments


  Note that this only works if the apps tries to retrieve bootloader status via Java. XPrivacyLua can't do anything if an app uses native code to check the bootloader.