Big Sur macOS 11.2.1 (20D74) is running from "APFS System Snapshot" – How to fix?

Question

The two volumes are present "Mac SSD" and "Mac SSD - Data". However, the "Mac SSD" volume is NOT mounted, but instead, an "APFS System Snapshot" within the Mac SSD volume is mounted and seems to be where macOS is running from.

How do I fix this?

How I Got Here...

• Yesterday I had ... 2018 15" Macbook Pro w/32 GB RAM + 2TB SSD running macOS 10.15.7.

• There has been a growing list of oddities, so want a fresh start NOT restoring from my TimeMachine backup.

• I created a new APFS Volume and called it "Mac SSD"

• I installed Big Sur 11.2

• Started to install all my software and data

• Booted back to Catalina and noticed odd drives on my desktop

• Checked Disk Utility, booted back to Big Sur, Checked Disk Utility

And here I am ... very confused.

Answer 1

It turns out that the snapshot is an intended security feature of macOS 11 and higher.

Answer 2

M1 MacBook Air, macOS Monterey 12.4, never reinstalled the OS, Time Machine disabled, but still shows that it is running from a snapshot:

Also, if I actually check disk snapshots from Onyx or terminal, it says that there are none:

I don't think this snapshot is somehow created by the Time Machine, but rather it might be created by macOS update utility to restore to the previous version if update goes wrong. Although I do not have any real evidence to prove this point, I'm quite sure you shouldn't be worried about your macOS setup not being clean or stable.

Sorry for my English, not a native speaker.