I don't know if this helps much, but I've read and augmented this analogy a little bit to help understand
Waboku.
When your opponent declares an attack on a monster, pretend like both of your monsters are going sitting at one of those carnival games where you have to use the mallet and hit it hard enough to ring the bell. Each monster must meet or exceed a certain value in order to "win" and destroy the opponent. Remember, each monster gets to take a "swing" at this point to evaluate things.
Let's look at a classic example Player A has Mobius and Player B has
Gemini Elf. Player A declares the attack on Player B. Player B responds by activating
Waboku. Now let's see what happens...
I'm going to do this in an "order" even though this typically happens simultaneously for damage calculation. Player B (
Gemini Elf) is given the mallet and is instructed "Hey, you gotta wack this mallet to a level of 2400 or above in order to beat Mobius."
Gemini Elf takes the mallet and swings. However,
Gemini Elf only reaches a value of 1900, so alas, Mobius isn't destroyed.
Mobius is then given the mallet and is instructed "Okay, now you have to wack this mallet to a level of 1900 or above in order to beat Mobius." Mobius smiles but just as Mobius goes to swing down,
Waboku comes out of nowhere and pulls the mallet out of Mobius' hands. Mobius swings down but hits nothing, 0. As such,
Gemini Elf gets to live too and we end the game.
Now if you take this analogy to
Gemini Elf vs.
Archfiend Soldier, you'll see why the turn player's
Gemini Elf is still destroyed when the opponent activates
Waboku, and no battle damage is inflicted. Its not that
Gemini Elf had his attack reduced to 0, its just that the "threshold" that needed to be met wasn't there.
From here I think you can apply this analogy to
Shining Angel vs. Mobius and you can see how the outcome is as has been explained.
I know this was rather wordy, but I hope it helps you understand the mechanics of
Waboku a bit better.