Those little cricket clickers were still popular when I was a kid, they don't sound remotely like anyone working the bolt of a Mauser, or any other rifle bolt being worked.Isn't it a myth that the crickets that were given to the airborne troops and used on D-day mimiced the bolt of the german rifle and led to us deaths?
Even if the sound was similiar, how many troops would be that familiar with how a Mauser bolt sounds, and really anyone waiting in ambush is going to put a round in the chamber well before there's any hostiles around, and engage the safety, maybe.
Whoever made up that little myth has seen too many movies, where the enemy has to work his bolt when surprised. In real life, any troop would already have a round chambered.