They DO use bad paste. It’s the ONLY reason people who change their thermal paste on their FAT PS3′s still get YLOD.
I’ve had a FAT CECHA before, I removed both IHS’s on it, changed the thermal paste and boy did it run cooler. (Naturally I did put the IHS back to make contact with the heatsink but I didn’t actually glue them back, I let the paste keep them in place)
Yes, Sony can avoid that problem by using better paste, but the problem is that they don’t want to.
IMO, IHS’s should only be used on PCs. They are useful there, because of people building their own PCs, and you normally don’t keep the same PC for more than five years at most (and most of the time less than that). However, this isn’t a PC. These are devices that are being built only in Sony factories, people don’t build their own PS3′s. Also, a game console should last much longer than a PC, and using IHS with poor paste goes against that. (Then again, they could have done that on purpose…)
And on a system that’s supposed to last at least 5-10 years, the paste they used on the IHS is of too poor quality. People who can disassemble PS3′s should be able to replace the stock thermal paste to make their system last longer, which IHS doesn’t allow.