AMD are not better. They’re probably worse. They’ll be looked at when the Intel tree stops bearing fruit. But finding an Intel bug is higher impact, so that’s what researchers want to look at.
This argument makes zero sense and fails real world inspection. You see, researchers did publish the fact that it affected AMD on Spectre.
For this vulnerability, they were unable to reproduce the bug on AMD (their words). Which means that they tried.
Consider you've got two sets of vulnerabilities: [1, 2, 3] and [2, 4, 5, 6, 7, 8].
If I label set 1 Intel, and set 2 AMD, then you can see how doing your research on Intel first will make it seem like Intel has 3x the vulnerabilities as AMD - even though it actually has half.