There is a problem pending with interlanguage links. Some wikitionaries lack the interlanguage link to greek wiktionary although there is a page.
examples include https://pl.wiktionary.org/wiki/%CF%87%CF%84%CF%85%CF%80%CE%AC%CF%89, https://en.wiktionary.org/wiki/%CF%87%CF%84%CF%85%CF%80%CE%AC%CF%89
When the "title" in polish wiktionary was created the English wiktionary momentarily "included" the polish title, but both English and Polish wikitionaries still do not have links to Greek wiktionary. You can also track the discussion [https://en.wiktionary.org/wiki/Wiktionary:Grease_pit#the_mysterious_disappearance_of_an_interwiki.
Is ti possible that el.wiktionary lacks «something» in software that «exposes» their data to Wikidata?
el wiktionary link: https://el.wiktionary.org/wiki/%CF%87%CF%84%CF%85%CF%80%CE%AC%CF%89