Yes, I am really sure. :) It says angle of aircraft not antenna and follows how this pitch range is used to show "above", "under" targets in reference to a/c nose angle.
There is no direct explaination given for the symbols, unfortunately. It says further in text that with activating low altitude switch, limits the lower zone to 1,5 - 2degrees above horizon. So no, from this text, one can conclude that FOV shrinks in vertical.
Zones are defined in text as in search mode to be 60deg azimuth, 20deg elevation. However when it talks in detail, it mentions +17 and -1.5 elevation regarding the horizon.