It's Windows, so I stupidly was goaded into installing the "Intel Driver Assistant" which checked everything, installed what it believed to be outdated drivers/packages, rebooted, then carry on.
528491 My user interface at the Intel ethernet upgrade section for my I218 looked nothing like yours. My entries were all stacked and there was no lovely pane like your picture. But I did download the x64-proset package--it's sitting on my desktop.
Also, fast boot was never enabled (unchecked) so not a factor.
So I did something guaranteed to wreck Solus ethernet: power down Windows and boot into Solus.
This time nothing bad happened and my ethernet services were not shut off.
Conclusion: Intel Assistant did something positive by accident or nothing happened at all, Windows just didn't feel like wrecking Solus today.