Another selection bug/feature ..

Select several tracks in Track view, open them in a Floated PRV window.  
 
In Track View, select a different track and open that track in Floated Event List. 
 
Return to PRV, ensure that the "Track Pane" is open so you can see what tracks are involved in the PRV group. 
 
Choose (or create) a moment in time when there are events both in the group of tracks in the PRV and in the single track shown in the Event List.  
 
Select a group of notes in PRV by Right-Click, Drag in the notes pane. 
 
Observe the PRV time line -- it shows a shadowed selection area corresponding to the notes selected.  Now, the issue:
 
Attempt to make the area shown in the time line in PRV longer:   left-click, drag, in the PRV time line, so as to include another note.    
 
BUG/FEATURE:    the PRV events are selected, but also events, NOT in the PRV, but shown in the Event List -- are selected.  The unfortunate consequence is unintended changes to events that may be hidden or unobserved, since the EL view does not necessarily show the area selected unintentionally.  

No, when you select a slice of time, you intend to modify or copy everything within the section -- WITHIN THE TRACKS CHOSEN.   The point is not whether or not you can see it, but that selection within the PRV can reach out and get stuff on tracks that are not even included in the PRV.