I don't have a definitive answer, but this is my experience...
Firstly, I don't think there is a 'Public Senseboard' per se. Your public URL makes publicly visible any and all senseboard tabs that have sensemeters that have been 'made public'. I.e. if you change the app position on your 'private' view it changes the 'public' view (as you have found).
I keep it simple. I have one tab which is public and all apps are made public, so what I see is what the public viewer sees. If I really wanted additional sensemeters in my private view I could add and position them after the publicly visible apps had been positioned. If I don't change the relative positions of the publicly visible apps, the public view would not change.
I think your suggestion would be a "nice to have"
HTH,
Roland