It may have better thermal conductivity but the solder paste layer is many times thicker, which offsets most of the benefits. That's why OC fanatics still delid them so they can lower the IHS by 0.1mm or ditch it altogether.
It doesn't. The black silicone you see around the edges of the cpu in the pictures is used to seal it.
From Ivy Bridge to Coffee Lake, the paste Intel used between the die and IHS wasn't the best thing at transferring heat, but what it had going for it was longevity.
The thermal layer is soldered because of better conductivity right? Than how it can damage CPU?