Thanks, @marcel21.
@gmcrozier So, thanks to
this thread, I've determined that this is definitely a basement related bug on these lots. It appears that any time you draw a structure that goes underground (basement, fountain, pool), a slope is introduced into the terrain around it. In most cases, the slope is incredibly small and tough to see, but it still tweaks the tiles that it affects. The Rattlesnake Juice lot is an interesting case because the slope is actually pretty dramatic and easily observable on it. Now that we've got the full scoop, I'll submit an AHQ report on it.