I thought it was strange that LRT was creating output with banding, when there was no banding in my original sub frames. I was sure that my 8 bit TIF export from Lightroom should have been processed without banding, but not sure how to get that result. Finally, I was able to do it. And it was a minor little thing! To get a nice smooth sky with no banding all I had to do was select Ultra High Quality output in LRT. I was using the default "High". Once I changed the quality, problem solved. A word of caution, I doubled the file size but I am indifferent to files size in my case. All I wanted was no banding, and I got it. So LRT CAN do it all
Sometimes you just have to try everything. The only problem is my sequences take such a long time to export and render, that I had hoped to avoid multiple iterations of making mistakes like that. oh well, its all good now. Thanks Gunther for your feedback.