Erase all content and settings requires reinstall of macOS

The "Erase all contents and settings" function in macOS is designed to remove all user data, settings, and apps from the system, essentially returning it to a factory-reset state. However, it should not erase the macOS operating system itself. The fact that this function has resulted in the removal of macOS on two occasions is unusual and not expected behaviour.

Here are a few possible explanations for what might have occurred:

1. User error: It's important to ensure that you are selecting the correct options when performing the erase operation. If you accidentally selected a different disk or partition to erase, it could have resulted in the removal of macOS.

2. Disk corruption: If there were underlying disk issues or corruption present before performing the erase operation, it could have caused unintended consequences during the process. In such cases, it's possible that macOS was affected or removed.

3. Software bug or malfunction: Although rare, it's possible that there could be a software bug or malfunction that caused the unexpected removal of macOS during the erase process. However, without more specific information, it's difficult to determine if this is the case.

To prevent this from happening in the future, consider the following precautions:

1. Backup your data: Before performing any major system operation, it's crucial to back up your important data. This ensures that even if something goes wrong, you'll still have a copy of your files.

2. Verify disk health: Use Disk Utility or other third-party disk utilities to check the health of your disk and repair any errors or corruption before attempting any system operations.

3. Be cautious during the erase process: Double-check that you are selecting the correct disk or partition to erase. Take your time and ensure you understand the options before proceeding.

4. Reach out to Apple Support: If you are experiencing persistent issues and unexpected behaviour with the "Erase all contents and settings" function, it may be worth contacting Apple Support for further assistance. They can help diagnose the problem and provide guidance on how to avoid this issue in the future.

Remember, performing any system-level operations carries some risk, so it's essential to proceed with caution and have backups in place to mitigate any potential data loss.

Erase is erase. That's the design spec. If you wish to not erase your drive, do not run any evolution that purports to do that.

Erase your Mac - Apple Support

https://www.easeus.com/computer-instruction/erase-all-content-settings-mac.html

What Does Erase All Content and Settings Do

Erase All Content and Settings on Mac is a powerful option also known as the Erase Assistant. This helpful option can help Mac users erase Mac devices and restore them to factory settings. Erase Assistant will guide you to erase all the settings, data, and Apps safely and efficiently. You should know that Erase All Content and Settings can only be used on macOS newer than macOS Ventura and Monterey.

I think in this context, "while maintaining the operating system currently installed" just means that the system will automatically download and install a fresh copy of that operating system, as part of the process.

"Quickly and securely erase" probably doesn't involve going through your entire SSD, file by file; or doing a low-level erase that zeroes the contents of each flash sector that makes up part of the SSD.

I believe that on an Apple Silicon Mac, or an Intel Mac with a T2 security chip, it causes the Apple Silicon chip or T2 security chip to forget the encryption key that it has been using all along for real-time encryption of all of the contents of the internal SSD. The data is still there, but unless you're the NSA or KGB and have plenty of time to kill, good luck decrypting it!

The machine then proceeds to perform a simple high-level erase that doesn't require zeroing every flash sector; just making notes that most of the storage on the SSD is now available to be erased, and reused, on demand.

Now you've got a "quickly and securely erased" SSD, but there is nothing on it. To maintain the previous OS (at factory settings, without your settings and apps), the machine downloads a fresh copy of that particular version of the OS from Apple, and installs it on the internal SSD. This would be a lot cleaner than trying to figure out all of the files on your previous (OS + apps + settings + data) installation that might have to be replaced/removed.

Yes, if you select that.