True, although it is easier said than done, especially from the driver's seat... and it takes a brave man to open lift bonnet and muck about with the air intake when the engine is roaring at max rev and engine bay is full of thick smoke. Of course, if you happen to be standing next to the engine bay with the bonnet up, and you happen to have a heavy piece of cloth handy, and you catch it when it just started, and you immediately understand what is happing - then yes, it is feasible. But in all other eventualities - not so much.
The other option, BTW, if to get the car against a wall, put it in gear and release the clutch - again, only possible is some circumstances, but it might stall the engine (assuming it does not burn the clutch).
The reality is that almost all cases of runaway Diesel engine end with the engine destroying itself, and/or catching fire.