An Asus employee gas mentioned that AMD has reduced the boost behavior of the Ryzen 3000 processors to a more moderate level as it was too aggressive and now is a bit more limited in favor of longevity.

It has been a bit of a discussion as to why motherboard differs in Boost frequencies with Ryzen 3000 on different motherboards. Now it is said by shamino (Asus employee) that AMD has limited the boost behavior in newer AGESA versions.

The motivation for this step would be that AMD apparently wants to ensure a longer life. As it says at least in the contribution of "shamino1978" in forums (via reddit.com).

"every new bios i get asked the boost question all over again, i have not tested a newer version of AGESA that changes the current state of 1003 boost, not even 1004. if i do know of changes, i will specifically state this. They were being too aggressive with the boost previously, the current boost behavior is more in line with their confidence in long term reliability and i have not heard of any changes to this stance, tho i have heard of a 'more customizable' version in the future"

As for the controversy surrounding the boost frequencies of the current Ryzen 3000 processors, have a peek here.

Ryzen 3000: AMD deliberately limited Boost behavior in favor of longevity, says Asus staff