Part of the development lies in Kane County, and part in McHenry County, and the article attributes the tax variations to differences in the assessment methods used by each county.
Further investigation is needed to know whether the different assessment methodologies account for all of the difference in tax bills. Perhaps. Perhaps not.
Many Chicagoland communities span several counties, and it's not uncommon for tax bills to vary - sometimes wildly - within a single community. Differences in school district, park district and other taxing body rates can result in homes of identical value in the same town paying very different amounts of real estate taxes. Homes in many communities, especially newer homes, lie within special services districts that pay taxes not levied on other homes in the community.
The takeaway - don't rely on a rough impression that a community has high or low property taxes. Investigate each home's individual tax bill carefully.