The problem with smoking on sentry/guard duty is simple. A cig shows up at about 1/4 mile with second gen soviet night vision equipment. You just can't take the risk.

The "False official statement" charge is something that goes without saying in a military trial. You are investigated, and if the statements the Marine made in his report to investigators are judged untrue by the tribunal, it's just one more thing to add to the list of convictions. Unlike a civilian trial, a court martial almost NEVER has one simple charge involved.