I have reason to suspect the bolded ruling is in error. The intended meaning, I believe, is to confirm that, even in the "imaginary" window in which Horn of Heaven, Solemn Judgment, Forced Back, and Royal Oppression are to be activated, the summoning player still has priority off the bat to respond. That is, you may Force Back or Solemnly Judge your own monster before your opponent may do so.Text:
Negate the Normal Summon or Flip Summon of a monster and return the monster to its owner's hand.
Rulings :
You cannot activate this card when a monster is Set.
If a monster with a Flip Effect is Flip Summoned and you activate "Forced Back", then the Flip Effect never activates.
If you negate the Normal or Flip Summon of "Dark Magician of Chaos" with "Forced Back", it is returned to the hand and is not removed from play.
You can activate "Forced Back" when you Normal or Flip Summon your own monster. You should announce this immediately after your Summon. Once you allow your opponent to activate "Torrential Tribute" you are acknowledging that the Summon was successful and you cannot activate "Forced Back".
So that's what I think the ruling means. But that's not what it SAYS. What it says is that if your opponent gets a chance to use a "real" card, then that automatically means you have entered "real" play and have passed that "imaginary" window for Solemn Judgment. What about all the talk of "YGO isn't a race" and "Priority is there to keep order" and "Just because your opponent jumped the gun doesn't mean they have a right to"?
Remember how, if you summon Cannon Soldier, and your opponent flips up a Trap Hole, you can say "Whoah! Slow down there! It's my turn; I summoned; I want to use my Cannon Soldier's Ignition effect!" and their Trap Hole will be returned to a face-down position? Well, why shouldn't the same apply here? Who says your opponent can jump the gun and play Torrential, thus cheating you out of your ability to Force Back your own monster? Aren't they supposed to wait until after you pass priority before they play?
:edit Yeah, and I'm using the words "imaginary" and "real" because I still contest the imaginary window for the activation of spell speed threes in response to a summon. But yeah...