HMD deadzones in cockpit on most aircraft incorrect

the HMD deadzones in the cockpits of almost every aircraft that has an HMD do not appear in the correct angles and mostly appear directly on the aircraft’s 3/9 line in stead of every spot where there isn’t a HUD.
the aircraft i found that do not have this issue are the US F-16C-50, Mirage 2000D-RMV, Kfir C.10 and the Eurofighters.
i’ve provided the JAS39C and Mirage 2000D-RMV below as example for what the deadzones look like on most aircraft (gripen) and what they should be (mirage)