Interesting, but I still don't buy it. The other article that the Forbes page cites includes a single case of slowdown on one iPhone 6. You can't draw any conclusions from a test case that includes just a single device.
Like I said, unless Apple is being misleading in their release notes, this patch ONLY affects Spectre vulnerabilities in Safari. The OS level vulnerabilities that could result in system wide slowdown have yet to be patched.
Obviously you can't which is why it was posted here. The intention was to draw users here to test their devices. Hopefully we coul have gathered enough data points to see which devices (if any) could have been affected.