Considering the ONLY item that can apply damage to enemies via a dash is the expert exclusive item Shield of Cthulhu(asides from the Solar Shield dash, which doesn't apply knockback to yourself. While it does apply knockback to enemies, it wouldn't work out as a feature if the intended design doesn't give you knockback, does it?), I wouldn't say this is worth the trouble to implement.
And not to mention that this is already rewarding enough on its own. You can use the dash to give yourself a boost in DPS while using another weapon or using the dash to take advantage of the invicibilty frames you get from successfully hitting an enemy. If you get launched from the ground when hitting an enemy with a dash, it would be more invasive to the purpose of the accessory than helpful because it would ruin the feel of it. Hitting an enemy and launching it back while I take some knockback in return is a perfect feel for the weapon(which can let you chain dash an enemy anyways, why would rising off the ground make this better?) Adding this feature for the sole purpose of an expert exclusive achievement would just add needless bloat, especially since no achievements in this game require the player to engage in an Expert Mode world.
