The glyphs of U+03CF..U+03D4, U+03D7, and U+03F0 are duplicates of basic Greek letters’ glyphs. U+03CF and U+03D7, the kai symbols, are kappas with descenders. The rest are specific glyph variants of the basic letters. See also ctrlcctrlv/TT2020#12.

For comparison, here they are in Nishiki-teki, along with the basic letters they look different from.

To be clear, duplication is not a problem per se. It’s fine that U+03D5 GREEK PHI SYMBOL duplicates U+03C6 GREEK SMALL LETTER PHI, because their glyph in this font is the one that U+03D5 requires. It’s just some of them that don’t have the right glyph variants.