Behavior of Image generate in 21.02 is not same as 19.07

I was planning to upgrade to 21.02, but something wrong.

In 19.07
I was configured "Target Images -> (2048) Root filesystem partition size (in MB) "
then after compiling, I will get an ~64 MiB .img.gz file, if I decompressing it, I'll get a ~64.1 MiB .img file, I can be flashing it via sysupgrade on device without issue.

In 21.02
the .img.gz file size is similar as 19.07, if I decompress the .img.gz file, I will get an ~2 GiB .img file, that causes I can't upgrade existing devices, because these devices don't have enough memory.

Why? How to fix that?
Thank you guys.

Unit changed, making 2048 (mb) = 2gb?

Unit didn't change. Partition size are same.