The search for workarounds to the Win7 Kaby Lake/Ryzen patch ban

Microsoft is carrying through on its threat to actively block Windows 7 and 8.1 updates on the latest Kaby Lake and Ryzen processors. Some folks are looking for ways to get around that block, and they appear to have had some success.
We knew this day was coming. A year-old threat from Microsoft that “Windows 10 will be the only supported Windows platform” on Kaby Lake and Ryzen processors re-emerged last week. A thread on Reddit reported that folks who had the nerve to use Windows 7 or 8.1 would be blocked from updates if their PCs had the latest Intel Kaby Lake or AMD Ryzen processors.
The blogosphere understandably went wild, even though nobody at that point had actually seen the block in action. That has now changed. Yesterday poster dave1977nj on AskWoody submitted screenshots of his attempts to install the “March 2017 Preview of Monthly Quality Rollup for Windows 7 for x64-based Systems” (KB4012218) on his Kaby Lake PC.

Of course I’ve long railed against installing Previews, and you’d be well-advised to avoid them, but the deeper question is what actually happened?