Indeed it is the failure of drivers to close up the whole train (together with drivers being released from the pits and speeding round to catch the back of the train) which makes the battenberg potentially as little use as a poorly managed/implemented safety car. (But at least with a safety car the driver has the possibility of enforcing a catch up by slowing right down.)
But (as I may have mentioned before
) neither is needed if drivers would just obey the yellow flag. Simples!
Regards
Jim