So this is Box Sync v4.0.5101 for Windows. Once the update was installed (acted just like previous updates), it started the location change right away pretty much silently. The first sign of it was I no longer had the "My Box Files" symlink (under Favorites in your Explorer window). It had a vague message on the app window but who really checks that? Once it's "done", it also popped up a message saying so. Again, without context you don't quite grasp what that means. The worst part is that the move was incomplete, probably because I had various things opened in applications. So I ended up having a bunch of folders that exist at both the old location (users/username/Documents/My Box Files) and the new location (users/username/Box Sync), and I had to manually move things over.
It's bad enough we can't choose the sync folder location - what if you want to store things out of the system partition? Now what's the point of moving the folder up one level? If anyone is like me, who uses Box extensively for protecting and sharing all kinds of files, you have a lot dependencies on the location: apps need to know where its stuff are, binaries need to have its path set, etc. With the relocation plenty of headache to reset everything, let alone the hassle of reestablishing the habit of saving new things to the new location.
Box is overall a good product for cloud based storage/backup, but this sync folder location issue is definitely a drag on usability. This recent change of location just made it even worse.