Granted the total throw explosive power is in the megaton range; but the individual warheads aren’t.
you are splitting hairs. Each one is half a megaton (which by itself is megaton class if you are not overly focused on word smithing).
Most significant targets would have 2-4 MIRVs delivered putting the total between 1 and 2 megatons.
That is a megaton class attack in my book and it would definitely leave a “big impression” so to speak...
So, I’m afraid your horse is now dead from the beating...have a nice weekend with these happy thoughts.