The Full Lock requires that you download an "MDM profile" for your phone. MDM stands for Mobile Device Management and it allows a secure third party to remotely manage the device. In this case, the third party is Flipd and it is remotely hiding your apps for you, but only you decide when this feature is activated. Flipd will only hide your apps if you explicitly enable the Full Lock. 

Is all of this necessary? Yes, because unfortunately Apple does not allow a third party app to hide or restrict access to certain apps without certain verified permissions.