The photo I saw was of a relatively flat, grass-covered lot with a few trees. It looked undeveloped to me and any fill would've been of modest proportions simply to level the lot.
There was no resemblance to an undrained "wetland".
I googled this case. From what I read, almost 50% of the lot was filled in with rocks and gravel.
That's probably because the photo you saw was an "after" picture.
As far as I know, no "before" pictures are available.