In all games there are rules in place to ensure fair play, and this applies to American Mah Jongg. Rolling the dice to break the wall is similar to cutting a dead of cards and prevents cheating.
We often hear players refer to the letter "c" displayed to the right of a hand on the NMJL card as a "closed" hand. The proper term is a "concealed" hand. Incidentally, some players refer to the "x" hands as "open" hand . The property term for this type of hand is "exposed". It is acceptable to use closed for concealed and open for exposed with no penalty incurred.
If a bettor chooses East as the winning player and East is lucky enough to have a Heavenly Hand after the deal, the bettor is paid as usual. This rule is not found in Mah Jongg Made Easy or any Bulletin.