The core issue is that we disagree on what the term
"sudden death" means in football. The only definition of sudden death in the NFL rules is for regular season games:
- Sudden death play — where the game ends on any score (safety, field goal or touchdown) — continues until a winner is determined.
The terminology
"sudden death" does not even appear in the latest rules for NFL playoff games; however, it seems that your interpretation is that sudden death means
as soon as a team establishes a lead in the game. That interpretation is not what appears in the rulebook.
However, I agree that if the Niners had not scored in their OT possession, sudden death would essentially be in effect upon KC's OT possession.