Counter-flu: "protecting virus"

Weird new countermeasure, claimed good against all flus:
http://www2.warwick.ac.uk/newsandevents/pressreleases/dipr/

They knock out most of one chromosome of a flu virus, making it harmless and non-reproductive. Supposedly it waits around. If another flu virus enters the cell, the latter provides the reproductive machinery for the protecter to replicate, and faster (perhaps because it has less RNA to copy after the knockout). This crowds out the new infector, slowing it down, and giving the body time to develop an immune response to the infector's surface proteins.

I kind of get the idea, but I also have lots of questions. Oh well.