there are urban (jungle?) legends regarding FMA all over the place. Some can be documented and some are good storytelling, you either believe it or not. Some of the ones I've heard of the top of my head...
"Leathernecks"
"45 Colt developed specifically for use against the Filipino Moros"
"Moro Kris swords cutting through a Springfield rifle"
"the ventenueve balisong"
"amazing stories of anting-anting"
"amazing stories of Hilot"
"supernatural accounts of heroics"
These facts or myths are not exclusive to FMA. I remember as a kid being told Filipino stories like "the lady of the highway", Filipino trolls (can't think of the Tagalog name), and many others. I think in the end, going by Filipino culture, its not if these stories are true or not, but are based on a belief system. The Philippines has been a somewhat suppressed culture, being occupied for so many years, so some stories served at the time, to keep the Filipino spirit alive and to give its people hope. Notice how most stories favor the glamourization of Filipinos? About how one man dispatched 29 foes with a balisong? About how the enemy had to create a leather guard to protect the neck? Rarely about how fearsome the enemy was.