Even if Flat Pattern Curves are turned off in Sheet Metal Preferences ->Flat Pattern Display tab, they are all visible in drafting Flat Pattern view.
Solution Flat Pattern Display setting of Sheet Metal Preferences controls the Flat Pattern view created in modeling space.
It can be understood by expanding "Model Views" and activating the Flat Pattern view in Part Navigator.
The control for drafting Flat pattern view is available in customer defaults under drafting.
i.e. Customer Defaults->Drafting->Flat Pattern View->Lines (Tab)
Hardware/Software Configuration Platform: INTL64
OS Version: 764