This circumvention of surveillance could work for current processors that assume they can trust the SPI chip. But it would be easy for Intel to package the SPI chip together with the CPU in future offerings, circumventing the circumvention.
I don't see any assurance for anyone that doesn't control the foundry itself.
Yes, Intel might do that, but "circumventing the circumvention" is practically describing Intel making the change as some kind of malicious/hostile actor that wants to facilitate you being the victim of a BIOS hack. I don't think that is what is happening, but the current architecture does have undesirable consequences. Rotkowska's proposal doesn't really "circumvent" anything Intel is doing - it mainly allows the end user to assert a clean BIOS state.
I don't see any assurance for anyone that doesn't control the foundry itself.