And you don't think that was in an of itself a balance of exchanges? In Small Favour Mab sends Harry into battle Uriel sends the Knights of the Cross. That's an equal balance if I ever heard one.
Balancing forces imply opposition. Two unrelated bullets fired at the same target do nothing to
balance each other.
Ghost Story the Favour was Uriel keeping Harry Soul Alive in Purgatory While Mab kept his body alive. Again both of their causes had been compromised by Harry's death.
That was not cooperation, Mab specifically stated that it pissed her right off that Uriel risked Harry that way. And ultimately Uriel's goal was to prevent Mab from sinking her hooks into Harry too much. This is not
cooperation, it is
competition.
Skin Game a repayment against the Denarians for their actions in both Small Favour and Skin Game in defeating their mutual enemy, all the while Mab gained power in WMD's of the Vault and Uriel got the chance to save multiple Souls through the actions of humanities Free Will. Including potentially Harry's.
Think of what Mac said to Mab "May your scales always return to Balance" "Flatterer"
All of those instances are about scales of balancing actions that have equal actions.
Plus I thought there was a WOJ about Skin Game being Mab clearing her ledger of favours and debts, which implied her favours and debts to Nicodemus, Uriel, Marcone and Hades. But I can't seem to find it and this hasn't been my day of misquoting hearsay WOJ's, so I won't use it in this argument.
It was stated right in the books that it was about balacing debts, but nothing that I know of points to anything involving Uriel owing or being owed any debts. The debts discussed were specifically Nic (both what she owed from way back and the vengeance from SmF) and Marcone (ie the SmF stuff), and to a lesser extent the skull for Bob and the diammonds as wereguild. With Hades, Harry surmised that Hades was complicit in the whole escapade by being Marcone's first "investor", but nothing about
debt, I figured part of his Armory role is to facilitate the occasional audition.