Yes. Gas convection ovens do not have a rear element, due to the nature of combustion. These gas ovens use a bottom flame that is located underneath the floor of the oven cell. The convection fan in the back circulates the heat coming up from the bottom. Therefore, air space of at least 1" on all sides must be left around the baking sheets or roasting pans.
Electric convection ovens use a rear element located on the back wall of the oven, which reaches each rack more evenly. Little to no air space is required around the baking sheet.