Hi Ben,
You do realize this question is related to my CSV Generator (http://toxcct.free.fr/polars/generator.htm), and not related to zezo in any case ? ;)
Anyway, the Help Section answers this (block "Generator Options", chapter "Interpolated") :
http://toxcct.free.fr/polars/help/csvgen_options.htm#_generator_options
If you noticed how the source polar data were from VR, we do not have the values for every angles and every wind speeds.
that leads to potential errors when it comes to generate the CSV with some but not all of the sails.
If you want to see what it does, select some sails (it doesn't matter which ones), and then click that option, and notice how the vertical and horizontal scales of the generated array change...