The movie had little period flavor. Even critic Leonard Maltin said this.

The book had this for what it is about. Gene was real Phineas was imaginary and the more daring side of Gene. One hint the two are really just Gene is the height of the two 5'8 and a half. Strange for two roommates to be the exact same height.Also, when Phineas did that exercise hit and Gene commented how only the two knew Phineas had succeeded. Gene suggested bringing in a coach the next day who would time with a stopwatch or whatever. If Gene had done so and Phineas's name had replaced A. Hopkins Parker on a plaque that would have been a sign Finney was real. He was not. As Gene graduated Finney was dead because Gene was now more daring and ready to face the world.

Gene was remembering back to when he was at the Academy. In actuality in the 40s Gene may have acted schizo and when he got daring he used a different voice and called himself Finney ( like Dom Deluise's character in ' Canonball Run' calling himself 'Captain Chaos'). This could be how others were talking to Finney. Later in retrospect, Gene recalled the whole thing as if his altergo had been actually another guy.