"By sending an email that repels all but the most gullible the scammer gets the most promising marks to self-select, and tilts the true to false positive ratio in his favor."
Basically the scammer needs to reduce false positives (email recipients who are unlikely to become victims) and adding some outlandish detail ensures that only the real fools will be fooled.
Reminds me of a school class mate who had a very low success rate with girls, and switched successfully to better odds by a similar strategy: "If you talk about you, and your life, and where you come from for ten minutes, and she is still there listening, then you know you have a chance."