My understanding is that because of:
and the safety measures built into Rufus, we get the error that prevents creating the bootable USB drive.First of all, I need to point out that, as many people have found out, 10547 introduced a major regression with safely ejecting USB drives - If you look into the insider build feedback for 10547, you will see that many people report that safe ejection of USB drives is broken in this build, as you always get the message "device is in use". This behaviour, which has nothing to do with Rufus, is the actual root of the problem.
In my not so humble opinion, when an application has worked flawlessly for many, many builds of Windows 10 and suddenly no longer works, it can pretty much deduced that something drastic has changed in Windows 10.
Just as we've all experienced our audio and video drivers no longer working, so it follows that Windows can break pretty much anything it wants to.