Has a FIBA World Cup game ever ended 55-51?
Exactly once. On February 25, 2022, Tunisia beat Cameroon 55-51, and no FIBA World Cup game before or since has ended that way. When it happened it was a scorigami, the first 55-51 in league history.
That makes 55-51 the 475th most common final score out of 1,178 that have ever occurred in FIBA World Cup. One point away, 56-51 has happened never and 55-52 has happened 1 times.