If you're delayed, you can't attack. It's just wordplay. The effect is the same. Delayed just makes more sense overall.
But please define "Can't attack." Say, a delayed creature with adrenaline can attack over once a turn, which in result means it will attack. If this card is meant for the creature not to attack at all that turn, not even by adrenaline, then it's different and should be probably placed at "Notes". (All this turn/attack can create confusion.)
If it is just "Delayed", then that means one counter, and then this is just an Iridium Warden for Light - Except it costs three more quanta, has less health, has one more attack point, and can't damage target creature. If it is full stop, then yeah.
