Samsung has touched the heights of hypocrisy already. They also touched the height of chopping out core Android features as well. And as you have read the title, yes, Samsung still doesn’t support Android Seamless Update on their latest flagship – Galaxy S21.
Android has this feature since Android 5. And even then Samsung didn’t implement the feature to date. The use of A/B partitioning, which does cost some storage space, most probably greater than 3GB. This benefits the update process, making it faster. During the update, you keep on using the phone, in the background, Android updates automatically. Once you restart, the new system files will be swapped between the partitions.
Previous leaks of the internal documents from Google suggested that A/B will be made mandatory starting Android 11. But they backed out pretty soon.
But everything shrinks down to the question “Why Samsung is not giving A/B partitioning ?”.