Hi Jim,
Excuse me for delay with answer.
You don’t see the unfiltered_html capability at the list of core capabilities as URE marks it as the “deprecated” for multi-site. Turn on the “Show deprecated capabilities” checkbox and you will see it.
The option “Enable ‘unfiltered_html’ capability” force this capability to work. It will work for those roles only, which include it. That is if you have ‘unfiltered_html’ capability turned on for the “Administrator” role only it will work for the “Administrator” role only.