In V5, even with Always pan parallel views selected, you could override this with Ctrl + Shift + RMB and tumble about, then subsequent RMB in that view would still pan instead of tumble. This seems to be lost in V6. Any chance of getting it back?
This was changed based on user feedback to make it harder to accidentally rotate the view. Here’s the youtrack item: https://mcneel.myjetbrains.com/youtrack/issue/RH-18483
You can still kickstart rotating the view with Control+Shift+arrow keys. Does that help?