You're kind of right, but it's not quite exactly the same. Armor can be pierced and shattered by certain moves unique per character, making armored moves risky if your opponent uses a move that can ignore armor. Additionally, armor doesn't quite work in the same way as invincibility as armored moves still have an active hurtbox while armor is up. There's hitstop, allowing someone time to react accordingly if they end up hitting into armor, and it's not counted as a whiff like it would be against an invincible move.
If you want an even more technical example, because armored moves still have a hurtbox, they have the ability to put a player at advantage against or even possibly beat a safe jump attempt at the cost of meter, while a typical DP would lose to it.