Agreed, sorry for the noise, even for the following noise too.
Only to make some xfocus", following OCCT terminology, closed is not periodic?
In the past Chris_G probably has tried to explain some of the difference between BSpline terminology used by FreeCAD/OCCT and the usual explanation around, sadly in the source of OCCT is cited a publication saying that is following this convention (as usual if my memory is not too broken) but probably it is an old printed book.
Sadly now I'm not at computer, but after some experiments even with degree 3 it will not worsen a lot with second form in my post, tuning the algorithm as the little extract from the help() result seems to show.
I'm interested in this sort of thing too, so I've made some experiments by trial and errors, so a better knowledge of the three parameters will be interesting to know.
I wonder if in OCCT sources or blogs or forum there is some focus on these things, I will try to make some research asap I've a computer available.