I'll be the guy who says that. RVU requires the sending device (DirecTV box) decode the source stream, overlay the video and audio and reencode the output into h.264 and AAC (I think AAC). The DirecTV boxes other than the HR34 lack the hardware required to decode video, composite it and then reencode it into h.264 on the fly.
If anything is being done to the source audio/video data at all, IMO, the HR34 is decrypting the source stream and re-encrypting it, though I'm not even sure it needs to work that hard. I say this because the RVU LAN clients are probably authenticated before
they're allowed to communicate with the HR34 at all, so re-encryption may not be necessary from a DRM standpoint.
My guess is the HR34 is just overlaying the RVU GUI when required, not terribly processor intensive. So if in fact the HR2x's are not capable of RVU, it wouldn't be because the HR34 has superior processing capabilities. If the HR34 does have a faster CPU and more memory, that extra horsepower is liekly being utilized to manage 5 tuners worth of scheduling and prioritization, and the ability to serve and manage up to three simultaneous client video streams with trickplay.
BTW, I believe the processing horsepower required to re-encode H.264 in real time at the 8mbps-10mbps DirecTV MPEG-4 bitrates can probably only be found on the dedicated encoders DirecTV themselves use to transcode network source MPEG-2 feeds and uplink them to the satellites. Just my .02.