SIMPLE: Does a "factory reset" ALSO perform a "OS reinstall"

Apologies, but it is not clear from support URL below whether a Factory Default (2) process also performs a OS Reinstall (3).

From https://kb.netgear.com/20898/ReadyNAS-ReadyDATA-Boot-Menu

"Your storage system has the following boot modes:

1. Normal. Initiates a normal boot process, just like booting using the Power button.
2. Factory default.

   WARNING: The factory default reboot process resets the unit to factory settings, erases all data, resets all defaults, and reformats the disk to X-RAID.

3. OS reinstall. Reinstalls the firmware from the internal flash memory to the disks. The OS reinstall boot mode can be useful when the system crashes and corrupts some configuration files. OS reinstall boot mode also resets some settings on your unit, such as Internet protocol settings and the administrator password, to defaults.
4. Tech support.
5. Skip volume check. (RAIDiator only)After a system crash, the system tries to scan and fix the volume using a file system check. If several problems are found on a disk, this process can stall, causing the system not to boot. You can use this option to skip the scan and let the system boot.
6. Memory test. Performs a memory test. The pass or fail result is reported using the unit's LEDs. Contact NETGEAR Support to interpret memory test results.
7. Disk test. Performs an offline full disk test. This can take 4 hours or more, depending on the size of your disks. Any problems are reported in the RAIDar discovery tool."