Hi Ivan,
I'm curious. Did you do or know somebody who did as much research on AMD
processors, as was necessary to find these vulnerabilities? If not, how
can you make such comparisons?

Here [1] is a official AMD paper on the speculation behavior in AMD architectures. Intro:

This document provides in depth descriptions of AMD CPU micro-architecture and how it handles speculative execution in a variety of architectural scenarios. This document is referring to the latest Family 17h processors which include AMD’s Ryzen™ and EPYC™ processors, unless otherwise specified. This document does necessarily describe general micro-architectural principles that exist in all AMD microprocessors. AMD’s processor architecture includes hardware protection checks that AMD believes help AMD processors not be affected by many side-channel vulnerabilities. These checks happen in various speculation scenarios including during TLB validation, architectural exception handling, loads and floating point operations.

Thanks,

Rudolf

[1] https://www.amd.com/system/files/documents/security-whitepaper.pdf