Okay, got this verified and can explain the confusion. I've also updated the game guide to better reflect what Sharper Blades does, how it works and what it affects.
Old Desc: The first combat technology increases the damages dealt by blade weapons, each level in this technology will increase by one the damages dealt by all units using bladed weapons (arrows are not considered to have blades).
New Desc: The first combat technology increases the damages dealt by blade weapons; each level in this technology will increase by +1 the attack dealt by all units using bladed weapons. This bonus applies to melee OR short-range (units with both melee/short attack, only the short attack will get the bonus). The bonus does not affect long-ranged attacks of any kind.
Racial Notes: Catapults are not affected, as they deal only ranged damage. Units with both long-range and melee, such as Balista or Axe Thrower, are buffed only for their melee attack. Units with both melee and short-ranged attacks, such as Dwarf Runners or Human Knights, will receive the bonus only for their short attack.
So that's it, only melee or short get the buff, units with melee/long-range would only benefit the melee, units with melee and short-range would only get it in the short-range, etc.
