[NTG-context] \setupsection ... works how?

Hi there, while replying to a post on comp.text.tex I made the interesting discovery that \setupsection[section-2][conversion=Romannumerals] cannot be replaced by \setupsection[chapter][conversion=Romannumerals] even though chapter is section-2 ... why is it? Shouldn't it be possible to use those names? -- Giuseppe "Oblomov" Bilotta