Yes it's a widely known exploit but only available for a very limited amount of countries.just watched ur 1st 5mins of the uploaded youtube video and felt disgusted about that idea exploit (building 5 squads of infantry and then cancelling it in order to get the "accumulate money" and "manpower recover" achievements. )
Now my next question is (since i just found out about it..), is that a widely known exploit and do you people really enjoy doing it ? ;//
If it's any comfort we didn't really need to do it to win that war it just sped things up a bit.
Also there aren't any other exploits used in the game except for the diplomat trick