As for your comment on process isolation. I believe it's because Spectre was never about getting info from other SEPARATE processes. It was about getting info from mapped pages that weren't readable to the current process. Like ring-0 code reading something vs ring-3 code reading something. As long as none of the other pages from that process were mapped into memory of the second process then I don't think Spectre affects things like this. The reason Chrome does process isolation is so that if someone gets code execution in a rendering process or such then it won't be able to read things like cookies or the page contents of sites that weren't from the same origin as that rendering process.