You may if you wish. Using the Windows uninstall process for SONAR (like most Windows uninstall processes) does not remove user created files.
 
That said, it is not necessary to fix this issue. Only you know what software has been installed. I am guessing that a newer version of the "Shared Utilities" was installed and based on that suggested a method of restoring the 8.5 version.

I'm in the mood for a fresh start (or a new program!) I've been looking at Studio One.
 
I can't think of anything that would have disturbed the Shared Utilities folder, though I sometimes checkout a trial version of something, it may have been affected unbeknownst to me.
 
Edit: Can I avoid reinstalling all the plugs by moving those folders and copying them back afterwards?