FileVault doesn't encrypt disk

Hi,

I'm on a 2020 Apple M1 Mac Book Pro, 13inch with a 512GB SSD. I'm running Big Sur 11.6.2.

I've tried enabling FileVault in the Security and Privacy options. Once I click 'Turn On' I'm given my passcode and then it immediately says it turned on - no waiting for the disk to encrypt (see image below which appears immediately).

I've checked Disk Utility which says it's encrypted.

However, I ran diskutil apfs list from the terminal and I get the output listed which is hard to interpret.

I've tried this using my old account, then I erased my disk and reinstalled Big Sur (but not my old account - I'm trying to do a cryptographic erase before I sell it).

Can someone please help me ascertain whether I've enabled File Vault or not please?

Thanks in advance!

APFS Containers (3 found)
|
+-- Container disk3 754AAFFC-E14E-41CA-8BAF-6840A61F6180

    ====================================================

    APFS Container Reference:     disk3

    Size (Capacity Ceiling):      494384795648 B (494.4 GB)

    Capacity In Use By Volumes:   33013383168 B (33.0 GB) (6.7% used)

    Capacity Not Allocated:       461371412480 B (461.4 GB) (93.3% free)

    |

    +-< Physical Store disk0s2 2F9E0678-C0FE-4627-BC31-E7B413939816

    |   -----------------------------------------------------------

    |   APFS Physical Store Disk:   disk0s2

    |   Size:                       494384795648 B (494.4 GB)

    |

    +-> Volume disk3s1 97E1B75D-F163-4144-A3F4-175A7885B5EB

    |   ---------------------------------------------------

    |   APFS Volume Disk (Role):   disk3s1 (Data)

    |   Name:                      Untitled - Data (Case-insensitive)

    |   Mount Point:               /System/Volumes/Data

    |   Capacity Consumed:         16220225536 B (16.2 GB)

    |   Sealed:                    No

    |   FileVault:                 Yes (Unlocked)

    |

    +-> Volume disk3s3 A89B4528-B3E6-4F79-B653-6AA05C830D13

    |   ---------------------------------------------------

    |   APFS Volume Disk (Role):   disk3s3 (System)

    |   Name:                      Untitled (Case-insensitive)

    |   Mount Point:               Not Mounted

    |   Capacity Consumed:         15321403392 B (15.3 GB)

    |   Sealed:                    Broken

    |   FileVault:                 Yes (Unlocked)

    |   Encrypted:                 No

    |   |

    |   Snapshot:                  CB401C7D-4AF3-44FF-AF47-3E144F9F6587

    |   Snapshot Disk:             disk3s3s1

    |   Snapshot Mount Point:      /

    |   Snapshot Sealed:           Yes

    |

    +-> Volume disk3s4 BA3A25C9-802F-4C96-B382-11A61A9EC4F1

    |   ---------------------------------------------------

    |   APFS Volume Disk (Role):   disk3s4 (Preboot)

    |   Name:                      Preboot (Case-insensitive)

    |   Mount Point:               /System/Volumes/Preboot

    |   Capacity Consumed:         230236160 B (230.2 MB)

    |   Sealed:                    No

    |   FileVault:                 No

    |

    +-> Volume disk3s5 38DA8B20-325F-4D69-811B-13FE6906DB48

    |   ---------------------------------------------------

    |   APFS Volume Disk (Role):   disk3s5 (Recovery)

    |   Name:                      Recovery (Case-insensitive)

    |   Mount Point:               Not Mounted

    |   Capacity Consumed:         1022619648 B (1.0 GB)

    |   Sealed:                    No

    |   FileVault:                 No

    |

    +-> Volume disk3s6 CB7FE97B-C270-4D22-82A7-F6A7FB12A2AE

        ---------------------------------------------------

        APFS Volume Disk (Role):   disk3s6 (VM)

        Name:                      VM (Case-insensitive)

        Mount Point:               /System/Volumes/VM

        Capacity Consumed:         20480 B (20.5 KB)

        Sealed:                    No

        FileVault:                 No