From the manufacturer of the R-27ER, I found this interesting note
The missiles pursue their targets in accordance with an update proportional navigation method both in the inertial/radio-corrected flight trajectory phase and in the semi-active homing phase after locking on target en route.
http://eng.ktrv.ru/production_eng/323/503/527/
As far as I can tell and this is only IMO, ED have not modeled the inertial/radio corrected phase of the flight of the R-27ER, I believe they have only modeled the semi-active homing phase. There was also a thread a long time back where the discussion was around whether the target would be alerted by a launch warning in the inertial/radio-corrected guidance phase and in that there's an interesting point made by Soviet:
https://forums.eagle.ru/showpost.php?p=1605987&postcount=28
Anyway, ED have stated that their engineer is working on improving A2G missile dynamics at the moment. Once that's done, their engineer will work on A2A missiles. There has been no update since. So one can only hope they implement the necessary changes to all A2A missiles.