Nacho,
The reasoning behind this is that every ring of a Painted Segment Bowl is going to be made up of a number of species and it is necessary to see the layout to avoid errors. All of the ‘field’ rings of a Feature Ring Bowl are made from a single species so there is no reason to have a ring view.
Likewise, every ring of a Tornado Bowl is identical. To make a PDF file where every page is identical is also meaningless.
If you you want to make an urn that is a feature ring bowl but you also want to paint the field rings using different species, this is not a standard procedure which means that you should use Woodturner PRO to design the vessel because you can do whatever you want to do because you are in charge down to the segment level. It takes longer to design, obviously, because in Segment PRO, the software does all the work for you.
As an option, you can design an urn in Segment PRO as a feature ring bowl for the feature group and as a painted segment bowl for the field rings so it is something you can do without leaving Segment PRO. As Mike would tell, you, though - Woodturner PRO is the best solution whenever you want to do anything that is non-standard. He even uses it to design his standard bowls because once you get used to using it, you can become very fast at it.
Lloyd