I imagine that if he were to confess any "I love you too" answer he recieves would count as a confession too.
Also any attempt to directly ask her to not confess probably has a decently high chance of making her either confess accidentally (i.e. "How did you know I like you?") or propt her to reject and confedd anywayd, since she doesn't know what's at stake.
Still 100% laying it on really thick with the plot device, but if there's any loopholes then they're not quite so wide.
For example one idea I had that isn't covered is getting her to transfer schools.