Samsung's 4 year android update policy could be just a marketing scheme. In real sense, the company may give only 3 major updates counting One UI 4.1.1 as One Major Update alone.
Quoting- "The Galaxy S21 series shipped with Android 11 and is eligible for four major Android OS updates. It is very likely that Sansung will count Android 12L as one, which means that the Galaxy S21’s last OS upgrade might be Android 14 instead of 15."
