In his wording, "affected" includes "partially affected". Boot Camp "undoes this", because the Apple disables all security under BootCamp.

No Thunderbolt security on Boot Camp. Apple supports running Windows on Mac systems using the Boot Camp utility [2]. When [doing so], Mac UEFI disables all Thunderbolt security by employing the Security Level “None” (SL0). As such, this vulnerability subjects the Mac system to trivial Thunderbolt-based DMA attacks.

However, on MacOS itself: Regarding Thunderbolt security, MacOS employs (i) an Apple-curated (device ID) whitelist in place of Security Levels [7], and (ii) IOMMU virtualization when hardware and driver support is available [1][3]. Vulnerabilities 2–3 (using the ID of a known-trusted device and forging DROM metadata) enable bypassing the first protection measure, and fully compromising authenticity of Thunderbolt device metadata in MacOS “SystemInformation”. However, the second protection measure (IOMMU virtualization) remains functioning and hence prevents any further impact on victim system security via DMA. The system becomes vulnerable to attacks similar to BadUSB [10].Therefore, MacOS is partially affected.