Mayan unique castle age tech ''Hul'Che Javelineers'' doesn't work as intended. In AoE2 DE second javelin always does 1 dmg regardless of what you are fighting against. In voobly however, second javelin also gets effected from the skirmisher's bonus damage against archer class and halbs. This means you can take out archers and halbs twice as fast. I ran some tests, Post imp Mayan skirm and a generic skirm vs arbalest w/o any armor. Mayan skirms literally just need 2 shots to kill it, while the generic requires 4. Consider trying it.

Probably everaoc thought that the arrow in Definitive Edition is not properly programmed. They added the second proyectile without looking if there was anything programed on it. First proyectiles use the unit stats and additional ones use whatever they have programmed, if anything.

I did the same thing on Wololo Kingdoms DE because I also thought Microsft did a mistake there.