It’s been a long time since I saw The Truman Show. The scene I remember most is where he got to the end of the “horizon” in the water.
I think it’s more a metaphor for the search for Something More when you think you have everything, than a test of bechira. He had bechira the whole time, but he had to develop the presence of mind to search/think “out of the box”. Someone in jail doesn’t have less bechira than someone out of jail, but their bechira certainly landed them there. That’s another difference – Truman wasn’t “incarcerated” because of HIS actions…