I’m not 100% sure I follow.
If I click in the UI on a track that has CS2 on it, then UC1 will switch to track and it displays the new track name on the UC1 controller. Of course if you click on a track that doesn’t have CS2 I suspect (I didn’t test specifically) that UC1 will remain on the most recently selected track. Thus as such the UC1 display cannot be relied upon knowing which track is selected. But given that Nuendo allows multiple tracks to be selected, such logic is limited anyway.