Stealth/VLO performance against SARH SAM/AAM

There is a strange notion which the Russians have with their SAMs and AAMs which results in the use of SARH/SAGG missiles, although ARH seekers are available.

I will concentrate on SAMs here because the developments there make the case more clear.
Russians have developed various active radar seekers for their SAMs, especially the BUK series and their very long range S-300 with 200km+ range missiles would be candidates for ARH seekers.
However, they stick to SARH seekers even for their new century designs, the S-400 and BUK-M2/-M3, where others like the French, Japanese went for ARH seekers (Aster, etc).

Either their ARH perform bad, or the illumination power of their engagement radars offer still more RF energy on target or there are other benefits for a SARH seekers.

I read much of “anti-F35” Dr. Carlo Kopps articles back when APA was active and I know that he has not many friends on this forum. There is a effect which Russian SARH SAMs have which he didn’t describe, which could increase their effectiveness against VLO/stealth targets significantly:
Stealth designs rely on deflection rather than absorption as the key physical effect for their VLO performance. Systems like the e.g S-300/-400 work in a bi-static mode with their SAGG/TVM guidance, means that the RF signal receiver is at a different position and at a different angle than the attacking illumination radar. The deflected RF energy may would not reach the emitting radar, but a bi-static SARH receiving seeker in the SAM that can attack from angle below the VLO target or above it and perform angle search pattern would have better chances to catch deflected RF energy, enabling a lock on the stealth target. This method would decrease the biggest problem with missile radar seekers, namely that they have to work in X-band, for which stealth designs are optimized and no effects like aircraft feature size can be used for improved performance (VHF-band).

One key element for this method to work, is a blind illumination capability of a portion of airspace (without actual track) based on coordinates from a radar system that actually detects the target. There is much debate about this; APA and Russians say that VHF band radars can see smaller stealth designs such as the F-35 like any other radar. Here on this forum some might say the F-35 has the same pie size in VHF-band as in X-band. We can take something in between, but a highly advanced IADS like the Russian one has assets such as the “Container” OTH system for early warning and coarse location, as well es high power static line of sight systems with very large apertures such as the Voronezh and Resonaz systems, with systems like the mobile Nebo-M acting at lower tiers. There is more, such as passive means, EO, IR, multi-static “trap” radars networks.
There must be rough target coordinated available for such a bi-static SARH engagement, with a accuracy as provided by multi-band systems such as the Nebo-M or single VHF-band Nebo-SVU, otherwise the RF energy of the illumination radar wont be sufficiently accurately concentrated on target (airspace portion).
The S-300/400 SAMs have robust missile up- and down-links, hence they would work with course updates via VHF-band target coordinates until terminal phase where the SARH seeker would try to catch illumination RF energy deflected to different directions by the stealth design.
The addition of positioning systems to the engagement radars of S-300PMU2 and S-400 could be a hint for the use of this method.

Hence I have the feeling that this described bi-static method directly benefits from the main function of stealth designs, RF-energy deflection, and could be the main reason why even the S-400 is still old fashioned SARH and possibly why the R-27 soldiers on.