They use a compound that is designed for longevity rather than performance, which is fine for the lower end of their product lines. They should be using solder for their 'k' versions and above imo.
When put between the die and the lid, the compound shouldn't age since it has no touch with any atmospheric air, it's tightly sealed there.
I have pastes with my CPUs (between the lid and the fan) which after 10 years are the same.
TIM under the lid should not age at all.
I wonder If some would be so forgiving if it was Amd using Tim and Intel solder?
No.
They cannot afford to, add 20c to a 4ghz 1800x and you'll be looking at the same we have with intel.
I suppose It's a good job they decided to use a superior method for their cpus so that their customers have a better more reliable product.
Solder cheaply gives AMD a competitive advantage and I think they promised this too - to continue using solder. They have never had any thought about changing it.