My guess is let's assume an A-10 is targeted by a Mig-21 in multiplayer. If that's the case, then they have to make a whole new icon for the RWR. Likewise the F-15 if it targets a Mig-21, the devs will have to design the Mig-21 icon as well. I'm sure there are other examples, but that's what I assume when they mean integrating.