Uh even this short stab is quite wrong. Here notes from Jolla itself for Sailfish OS 5.2
As promised, users can unlock the Jolla Phone bootloader. A corresponding menu item can now be found at the System Settings / Developer tools
Users can do factory reset from the System Settings
Users can enter the recovery mode with the volume up key + power key combination
Flashable images and fastboot will be provided (coming soon)
The initial version of the Privacy Switch was implemented. The function is end user configurable and to start with, the users can control e.g. Bluetooth, WLAN, Location and AppSupport status with the switch. Further implementations are coming and the framework is available for community contributions.
The base of Sailfish OS is a full blown Linux, way more open than Android (more options for the user, less secure than Graphene, which has that as main goal) you can easily install/compile Linux software on it.
Close source components are used. Parts of the UI (Jolla is open sourcing more and more), libhybris to run closed source Android drivers, Android App Support.
So yes its not as open source as debian, but offers more freedom to modify the OS than Graphene and gives you near full control.