Does the space from the wall to the AirPort Extreme negatively affect WiFi signal?

I am looking to upgrade from a AirPort Extreme (4th gen, "Mac mini"-like profile) which is vertically mounted, to a latest model AirPort Extreme ("tower") and like this vertical mount; however, I thought I had read the WiFi router antenna's should have some "space" (6-12") from the wall, else the signal in that direction will be negatively impacted. Is this true and, if it is, would this mount negatively impact WiFi signal in the direction toward the back of the mount (in other words, would the signal "behind" the front face of the router be negatively impacted?)

The intended placement would be on the eastern most wall, with nothing but a garage beyond it, so the question may be moot as long as the other directions are not negatively impacted.

Any insights would be appreciated, this mount seems like the perfect solution for what I want, pending the answer to this question.

Thanks!!!

Innovelis TotalMount Mounting System for AirPort Extreme and Time Capsule

Innovelis TotalMount Mounting System for AirPort Extreme and Time Capsule

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