Diegetic musicals have non-musician characters often burst into song, seemingly for no reason other than that it's a convention of the form. What is the veracity of this statement?

The statement describes diegetic musicals inaccurately. In such musicals, the songs typically emerge from the story world and are a natural part of the narrative, rather than characters bursting into song without reason. Characters in diegetic musicals usually express their emotions or develop the plot through song, and these musical moments are often motivated by the context within the story. Therefore, the idea that non-musician characters sing "seemingly for no reason" contradicts the fundamental principles of diegetic musicals, which integrate music and narrative cohesively.

The options which consider the statement to be true or conditionally true overlook the essential characteristics of the genre. A subjective interpretation of this style of filmmaking does not accurately reflect its conventions either, as diegetic musicals have defined rules about how and why music is incorporated into the story.