Exactly, but they describe as something more loading past that stretch of "bay" and the town itself.
It depends. It is possible that the journalist wasn't describing what we think or what he thinks he was actually describing. The way he made the statement it was too casually. If he actually knows the map by head he would have made an extra comment on how the map seem to be bigger than expected. I would have trusted anything like this more if it had come from CVG but even they have been confused before even though they do check the fanmade maps from time to time.
Even from the east of the Alamo Sea you can look over the Alamo Sea to a mountain and possibly see pops in from the canyon. Who knows if the guys from IGN actually know at all times which mountain is Mount Chiliad. Even on this forum I still see people who have checked the map make mistakes as to what mountain they are actually looking at.
And as to not showing any screenshot beyond the northern shore, what would be the point if there is nothing of note out there? It is logical to mostly show the south when dealing with Mount Chiliad since that is where most of the map is located. Looking towards Los Santos is far more interesting than looking out over the ocean when looking north.