Hi M8

I have already written about it. Google's operating system distribution policy.
The latest releases of the system are given to the biggest contributors but also the latest devices - mobile phones.
Devices that are installed in cars are among the last on the list for fresh operating system. Only a few on the market got Android 10.
NoName devices and the vast majority of Chinese are still on Android 9 or lower.

Fake Android builds are a well-known thing and among the more popular "modifications" with them :d
It can also be written that the Android version is 20! Even to make it look different

But what can't be faked is the API level. This is the only valid method of verification for such devices.


Edit:
How it is checked has already been discussed.

The simplest and fastest - install CPU-Z from play store.
Under the tab SYSTEM there is an item API Level.
You can check the rest yourself - googling. For example, API level 29 is Android 10.