Nah, there is some logic to what Shanahan was thinking.
Most people may disagree, but let's say things turned out different and played out exactly how Shanahan thought.
Then, the narrative here would be different. People may think.. huh, maybe it is okay to take the ball first in OT.
The simple premise was... both teams were matching points. Both defenses were good enough to keep each other out of the end zone.
So, if both held each other to a FG.. then SF would get 1st possession in "2nd" overtime to win the game.
Remember, KC only scored 1 TD in regulation time in Super Bowl. Held to 4 FGs and twice in the 4th quarter.
So 49er's D was doing their job.
I believe the "Math" in Shanahan's head was: the 49er D can hold KC to a FG. My offense can definitely get at least a FG. So, if take the ball first, then 49ers will win in "2nd OT"
The problem with this logic is that it is a passive decision. It does not account for the thought that you could win on your possession if you took the ball second. Even if both teams score a TD because you can go for 2.
If this game was more offensive oriented with TDs galore, I'm pretty sure Shanahan would have taken the ball second. Because now, you are thinking of ending the game with a 2 point conversion.. not wanting the other team to get 1st possession of "2nd" OT.