Genie garage door opener (screw type) - Rail moves

[Sasi Kumar]

Hi all, 

I recently bought a genie garage door opener screw type at home depot. I paid a contracting company to install it. However the garage door when is opening, the opener and the rail moves a little towards the garage door opening. When closing it comes back. Contrator said its normal as the rail is mase for flexibility to move. But wanted to get a second opinion if thats correct as in online videos i did not see something like this.

thanks