Part of TomsHardware's leadup to their 2400G/2200G review, they used their digital microscope to examine a part of the heatspreader, exposing its very uneven surface. TIM is only intended to fill in these tiny air gaps, as well as the same air gaps which exist on your heatsink, and why you don't slather it on like butter to toast, but instead use it sparingly.
Also they're going to be testing it with a Mini-ITX motherboard, an area AMD has been sadly absent in for a long time. Will be interesting to see how this setup performs. Not expecting miracles, RX 550 Mobile in terms of performance, but it's a start.