First, Sanyo only sells CD-RW drives in the OEM market, so you won't normally find a Sanyo branded CD-RW drive in the first place:
Second, HD-BURN is a relatively new technology that Sanyo is still trying to promote. I think they perfected it after they designed their last CD-RW drive, and it isn't something that can be added by a firmware update. Thus, only newer drives will be able to support HD-BURN.
Sanyo is actively trying to get others to license the technology, but apparently hasn't had much luck so far. Right now I believe only the Optorite DD0201 and DD0203 drives support HD-BURN, which is somewhat ironic since both are DVD burners and one of the touted features of HD-BURN is greater data density without the need for a DVD burner...