Thanks for the report, JeroenR.
However, this is the correct behavior. The ruling is that if an attack has opponents recive the next hex, the hex will be revealed, even if all opponent's are somehow protected (Guardian, Moat, etc.). I can understand that this is counterintuitive, but the general idea is that attacks need to work with however many players are unprotected, so you take (discard, reveal) the hex and then it goes in turn order who is affected or protected. Basically the effect doesn't "know" it doesn't need a hex until after it has to be revealed.
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