How can you verify when a drive was last formatted?

I'm not aware of what's causing that stat behaviour — are you using Big Sur? On a drive formatted with Catalina, stat reports the correct value.

In any case, you can use my tool Drat to see the timestamps of all APFS volumes. Do diskutil apfs list to find the block device that represents the "Physical Store", e.g. in the following output...

APFS Container (1 found)
|
+-- Container disk1 9FB9190C-8782-48FB-956E-0539C73996ED
    ====================================================
    APFS Container Reference:     disk1
    Size (Capacity Ceiling):      479894224896 B (479.9 GB)
    Capacity In Use By Volumes:   409366626304 B (409.4 GB) (85.3% used)
    Capacity Not Allocated:       70527598592 B (70.5 GB) (14.7% free)
    |
    +-< Physical Store disk0s2 44F7C60F-6302-4F08-A1A4-40F7BAA25D12
    |   -----------------------------------------------------------
    |   APFS Physical Store Disk:   disk0s2
    |   Size:                       479894224896 B (479.9 GB)
    |
    +-> Volume disk1s1 68FF83AF-C326-4C78-ABDA-C33E52D07D29
    |   ---------------------------------------------------

[...]

... the Physical Store is disk0s2, which corresponds to the block device /dev/disk0s2.

Then use Drat to inspect the physical store, e.g. drat inspect /dev/disk0s2. Included in the output for each volume is "Formatted by:" and "Last modified by:". All times are in UTC. For example:

[...]

Volume name:        ### macOS ###
Role:               System (contains a root directory for the system)
Flags:
- Volume is unencrypted.

[...]

Formatted by:
- ID: diskmanagementd (1412.41.1)
- Timestamp: Sat Nov 23 11:18:26 2019
- Last XID: 25

Last modified by:
- ID: apfs_kext (1412.141.1)
- Timestamp: Mon Feb 15 10:22:49 2021
- Last XID: 5d644b

[...]