If “Splice the Mainbrace” means “Issue the crew their allotment of rum,” what does a Captain say if the actual Main Brace needs repair? “No, no, I really mean it!” Or “…And when you’re through, have a work crew repair the standing rigging?” Or…?
Splicing the mainbrace is essentially an emergency repair. If your mainbrace was shot away during battle, or otherwise broke, it would be extremely obvious and often a life-and-death matter. If an actual order to splice the mainbrace was given, no one in their right mind would think it meant to have a drink.
Similar to “kissing the gunner’s daughter.” She’s not here, Dave.