This would be my first impression as well, but when I double-checked with the REG, I couldn't find anything to satisfy my enough in that regard. Good ol' Gates says AT ANY TIME, and all the REG has to say about it is:
"Add to battle abilities can only add cards to a battle in which you are participating. Adding a card to battle causes the player on that side of the battle to control the card. If a different player normally has Permanent Control of the card, the player on that side of the battle gains Temporary Control until the card leaves battle."
And all of that still adds up nicely with the idea that I could block myself with Gates.
Which leads me to the boards to inquire from the community.