The issue is that the Dash action doesn't, by itself, let you move. It just gives you "extra movement for the current turn". So the question becomes: is this ability intended to make it so you can move immediately as soon as Initiative is rolled but before your turn comes up in the round (assuming you're not first)? Or is it merely intended to make it so you can preload extra movement onto your first turn during combat?
If the intention is the former, then mechanically speaking the ability does nothing, because taking the Dash action outside of your turn doesn't let you move immediately. Hence why other abilities like Ready specify that you can move up to your speed instead.
If the intention is the latter, then it's fine. You roll Initiative, spend your Reaction to Dash, then when your first turn during the combat comes up, you've got extra movement to spend.