I previously offered an image that was taken behind the fence at Harry Grove Stadium. This one is a little closer to the fence (and where I found two of the balls). From the stands this area looks like one solid wall and when the stadium was opened the lower wall was the only one that stood. As they got more advertising apparently it made sense to add a second wall to accommodate. One can see how a home run will hit the far wall and then drop to the ground (I have seen a few hit hard enough to make it back onto the field).
As the creator of about 1,000 podcasts, it’s been my experience that when you give something away, you’ll get it back, and probably more. Before the additional wall of advertising was added I always thought that it would be a cool idea to place stands in home run territory. As this would be outside of the stadium, these stands would be available to anyone without cost, which would attract more viewers to the games. At first blush one might think that people who would normally pay to get in would just as soon take a crummy seat in the outfield, and while this would be, to some extent, true, if concessions were offered in the area then more money would flow in that way. With the addition of the second wall this idea becomes moot.
FWIW, I have been to many minor league ballparks, and very few have seats in home run territory.