It's not the only clue. There are reports that it consumes less power than the old models and it is also significantly cheaper than the older units, which implies cost reductions. When you add everything up, it certainly looks like it has atleast 65nm cell inside, maybe even RSX.
Heh. The forum hiccup granted this thread a reprieve, so I'll roll with it. I referenced one's thread in the main forum as an indication that the 40GB model has 65nm something (and the likely source of Dr Evil's and Bobbler's posts), hinted at by its lower power draw and weight (OK, this could be general streamlining, but it could also be smaller heatsinks [in the PSU, too], etc.).
SACD also requires special hardware in the optical pickup to be able to process the Pit Signal Processing signal from the disc. Basically, SACD's have some fancy copy protection in that there is a decryption key encoded in the width (not the length) of the optical pits on the SACD surface.
Perhaps Sony was able to lower the cost of their drives by not including support for this.
Alternatively, it may be that they have to pay some licensing cost to Phillips, and they just didn't want to do that.
It's a pity, because SACD support is actually pretty nice in the original PS3s.