The apparel that can be earned through apparel boxes have bonuses.
Some have bonuses that grant extra coins when they win. You're opponent was using this to get more coins.
You still don't lose any more than your entry fee when your opponent has this bonus.
You may already have apparel that has this bonus. From the main menu, click your profile pic in the top right, then Edit Apparel at the bottom to see what apparel you have.
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