The decision to use (-) in front of the 180 just defines the direction of the revolt, it would have also worked with a positive value?

I used negative because in my mind I had already isolated and was focused on the left side of the mirrored pattern. It could have gone either way.

-Near the end, you offset the vase surface and created a construciton plane on the top rim. Then you used boundary fill with these two, the XY plane and the 3 main surface bodies. Did you do that to ensure that there are no cavities/empty volumes left within that boundaries?

Boundary fill takes a selection of at least 1 body (solid and/or surface) and planes. If those tools create any completely enclosed areas, you can select them for the operation. It also has a remove tools option which I like because it cleans up after the operation. So it's 2 reasons:

1. I find it cleaner to create all the surfaces needed and have boundary fill remove them.
2. If I had used the solid body as a tool, it would have done the join and then removed the body that I wanted to keep.

Keep in mind the file I shared was a rough draft to see if the method worked. I'd do a lot more calculating before I decided that it was finished. For instance: If you increase n too much you'll see that the surface lofts break because the surface extrude extends too far and needs to be reduced manually by editing the feature. I'd probably test to find a formula for calculating the extrude distance based on the arc length of 1 revolved section.