The point of the will, as a game mechanic, is to allow players to out reads, reports, and tells upon death. Using it to confirm the cop via a code word in multicop setups (mafia doesn't have enough time to guess the word since the will is shown right at daystart) is, imo, abusive and against the spirit of the mechanic. Kind of like using crypto d1 to prevent the mafia from cc'ing the pr's later on, another such gimmick that is vio-worthy despite there being no specific rule against it.

TL;DR basic logic broken, vio cop coders to fix.