I believe that TOP_OF_PIPE_BIT is equivalent to ALL_COMMANDS only if used in second synchronization scope. If you use TOP_OF_PIPE in first synchronization scope, it means that the execution as continue as soon as top of the pipe is reached, which is before vertex, fragment and other steps.

So in first synchronization scope, ALL_COMMANDS is equivalent to BOTTOM_OF_PIPE and in second synchronization scope, ALL_COMMANDS is equivalent to TOP_OF_PIPE.

Feel free to correct me if needed.