Greek anarthrous nouns speak not of "the", but of the quality, character, and activiy (functionality) of the noun. There is no English equivalent, and the indefinite article (which is absent in Greek) has replaced the anarthrous. And that's the HUGE problem for the Englishizers.
So 2Cor 1:20 is not speaking of "the" promise, but of the quality, character, and activity OF "the" promise. Jesus Christ is, of course, that anarthrous for the articular promise.
This false doctrine (and most others) is because Englishizers don't understand the simple grammatical distinctions between donor and receptor languages in translation relative to noun forms. And since nouns do all the "verbing", and adjective are modifying the nouns while adverbs are modifying the verbs that nouns are "doing"; it means understanding the comparative noun forms between languages is possibly the most vital aspect of translation and comprehension besides the word meanings themselves (which are also nebulous in English until examined carefully).
But you likely already knew all of that, looking at your posts.