And it appears I figured it out. You can't have more than one Genre listed.
Evidently Genre must have only "classical" as its entry. Having more than one genre with semi-colon separation (ie Classical;Opera) doesn't work for anyone else that was wondering.
The reason for the "Classical Music can only have one Genre (Classical)" is down to the restrictions imposed by the JavaScript Routine/Function that determines if the current track is Classical or Not Classical. It can only use Genre=Classical when testing the content of the Genre field/tag because the word Classical can occur in the Genre for a Non-Classical Track, i.e. a Classical Crossover track.
Dawg - take a look at MC Ultra IIC, IIIc or IVC which like the ET Ultimate I variant have the Track + Album Info page as the 1st page, use the words Renaissance, Baroque, Classical, Romantic, Modernist, Postmodernist or Contemporary to switch into "Classical Display Mode and use the "Style" tag as the obvious repository for the Classical Music Composition Type - Opera, Symphony, Cantata, etc. If you click on the link at the bottom of my Forum Signature you can read about the MC Ultra TrackInfo Plugins and the ET Classical Music Tagging Method.
Although the format of the MC Ultra TI's is slightly different to that of the ET Ultimate TI's you should be able to copy any modifications/changes you made to the Blue Dream Track Info Template to the relevant place in the relevant MC Ultra TI's.
N.B. Don't forget that because the MC Ultra TI's are shipped with every MC32 update you will have to change the Folder and TI Name of your Version, the simplest way of doing that is to change the "ET" prefix to something else.