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The battle begins when the Hero enters the field of battle, not when the Evil Character blocks. If Jacob, ET or a green prophet with Hidden Treasures plays first, don't expect to "coward block" with Trembling Demon.
Since the question is whether or not any enhancements were played in the battle, which would be an end of battle decision, I don't see how the trigger/condition would not be reaching into the past.
... if we're going by the grammar on TD, ...
"If your homework is done by 8:00, you can have ice cream."If a kid did his homework before his parent said the above statement, he's entitled to ice cream, isn't he? Seems like the same thing as Trembling Demon.
I give up, I'm joining YMT for ice cream. We're in the South, it's still above freezing here.