Most kernel devs have Intel processors, and anecdotally, it does seem like you see more AMD-specific patches coming in the changelogs as people with the chips get new kernel versions and find new breakages.

Another side effect of Intel's market penetration is that the Intel implementation of any given featureset is targeted first. Things like nested virtualization may work mostly-OK on Intel by now but are still in their infancy on AMD; for example, it appears that MS still blacklists AMD from nested virtualization. [0]

[0] https://github.com/MicrosoftDocs/Virtualization-Documentatio...