I'm pretty sure that if you read again, it'll say that he didn't put the MEMORY heatsinks on. In that case, it might be OK if the RAM is not OCed.
BUT, the VRMs, Voltage Regulation Modules is a different thing altogether.....those NEED to be cooled for sure...
At manual controlled speed of 35% on my stock 5870, I get max temps of 54 celsius on the VRMs (3 or 4 VDDC readings in GPU-z) while gaming in BC2 for whatever duration of the gaming session. It's pretty good. The Accelero is know to let the VRM temp reach 100 degrees celsius or more.
If the Accelero's VRM sink is undersized/underrated, and the VRMs are running warm, who cares how cool the GPU core is...there is still a sub-system on that GFX card that is running pretty warm.
It's a sad situation...I DON'T understand how in the hell AC could have overlooked such detail, with experience on lots of Accelero coolers. They did the GTX-series (GTX 260, 275 and 285), the one for the 4870X2, the HD5970 model...plus the twin turbo, and all that JAZZ...
I guess their engineers are high on crack. (sorry, it's the ony explanation I can figure out)