Rockpi4b+ use Debin5.10 image but kenerl is 4.4?

I downloaded image from here:

and the official sites says it is 5.10 kernelDebian Buster Desktop (Linux 5.10),
but when i mounted this raw image, the kernel header is 4.4.194.
And where to download the real debian image with 5.10 kernel?

You can skip that and move to

As the official image it is so “weird”…armbian is a good choice, thanks…