To be honest, the world map idea makes far more sense. That's how that dialogue should have been displayed. In the revision they've made, you go into Junon seeing the canon still there, and then suddenly when you arrive at the area, it's gone. It doesn't work well for continuity.
Somewhere along the line it looks to me like they vetoed the world map exposition in favour of the field. And I think that was a bad idea. Further to that, I remember the first time I saw the junon cannon exposition- I thought "What's missing... I don't get it". If it had been on the world map, the missing canon would have stuck out like a sore thumb.
Unless the dialogue can still be seen somehow. I dunno. Maybe one day we'll have a world map script editor?