You can see the tree is actually skinnier below the straps than above.
(Note: I spoke with store management and he indicated he would talk to the gardeners.)
With fall comes a perfect time of year to plant young trees into your landscape. Conventional wisdom has changed over the years regarding supporting trees when planting. I would encourage homeowners to consult their local extension cooperative to determine best practices for your area of the country.
With that said, a tree grows a stronger root system and develops trunk taper when the tree is staked properly. A little movement when the wind blows can be a good thing. Remember to remove the straps once the tree can stand on its own.
UCCE Master Gardeners has a good page to consult.