Article gives English "many" and Korean "manhi" as an example of a false cognate.

I proposes that this may be a true cognate, in the light of Nostratic hypothesis. Let's start from English. English "many" came from Middle English "manye", Old English "manig", reconstructured Common Germanic "managa", Proto Indo-European "menegh", which meant 'many', or 'copious'. Reflexes in other Indo-European languages include Irish "minic" and Welsh "mynych", which mean 'frequent', descended from Common Celtic "minig". Also Russian "mnog(мног)" and Old Church Slavic "munogu", which mean 'abundant'. This is well-established and you can find it in PIE references.

On the Korean side, -i in "manhi" is adverbial suffix, so the root is "manh(많)". In Middle Korean this root is written "manhâ" (â for arae-a, first a is long tone). There are Written Mongolian "mandu" and Chuvash, a Turkic language, "mъnъ", which mean 'big', also attested Old Japanese "mane-si" meaning 'many', but replaced by "opo-si" already in the old time (from Old Japanese "opo" meaning 'big') thus results in modern "ooi(おおい)" but still meaning 'many', and Evenki form "man" meaning 'crowd'. This allows us to reconstruct Proto Altaic root "mana(ha)". This is more controversial, but can be found in literatures: Mongolian-Japanese relation pointed out by Ozawa Shigeo who compiled extensive Mongolian-Japanese dictionary, and also noted by Korean scholar Samuel Martin in "Lexical evidences relating Korean to Japanese", with sound correspondences and all. (Actually, since "m" and "n" is same in all reflexes, there's not much to do.)

This two reconstructed protoform can give rise to tentative Nostratic root "managha", and the rule that Nostratic /a/ gives PIE /e/ and loss of final vowel is regular. (See Allan Bomhard's book "Indo-European and the Nostratic Hypothesis") To get Altaic form you need to assume /gh/ becomes /h/ between vowels, which is reasonable.

You may disagree. But I think there are reasons to believe that m-n- for "many" is likely to have very ancient root, and English "many" and Korean "manhi" may be a true cognate.