I can confirm this directly. They aren't "seconds"- they are specifically designed and sold to the big-box stores.

I had a relative who was a salesman for a maker of power tools. There were too versions of what appeared to be the identical tool - but if you opened one up, you would find lower cost components (plastic gears, lower torque motors, thinner housings) as compared to the versions you might buy from a place like Grainger or Mc Master.

The model numbers are identical, but the serial numbers give it away - things like an "H" at the beginning or end of the serial number for "Home Depot".

Stihl will not change their tooling to meet big-box pricing, which is why you only see brands like Poulan and Black and Decker at WalMart - but you'll never see the pro version of Black and Decker (Dewalt). But even brands like Milwaukee are suspect - if you buy a Sawzall from a hardware store vs. a Home Depot, there's almost no way to tell - until you look at the warranty.