It will have been for a medium departure Pace they will have given a full stop then cleared the aircraft after the 2 mins.
Its pure bollocks mind because the Light aircraft will be touching and rotating in the first 500meters of the runway and the medium will be rotating in the last 3rd of the runway. The light aircraft will be turning crosswind beofre it gets anywhere near the wash off the medium. That is of course if it was a jet if they were behind a slab wing TP there is no where near the same amount of vortex but they would be near to its rotation point.