proverbial

Japan's Cultural Code Wordsの「目利き」(Made to Please the Eye)の項からです。
This reaction to imperfection was a symptom of the mekiki syndrome that is deeply embedded in the Japanese psyche. They were so used to having everything made so finely and detailed so meticulously that any variation stood out like the proverbial neon sign.
"proverbial" は知っている単語 "proverb" の形容詞のようですが、ネオンサインを形容する意味は何でしょうか？
辞書を見ると諺の形容詞の意味もありましたが、次ぎのような意味もあることが分かりました。
・Cambridge English Dictionary: well known: his proverbial good humour
・Macmillan Dictionary: well known, or typical: the proverbial veteran actor Kirk Douglas
・Vocabulary.com: widely known and spoken of:
If something is proverbial, it is from a story or saying that is well known. The proverbial Fountain of Youth will make you forever young. The proverbial Pie in the Sky is where your wildest dreams come true.
Proverb is the root of proverbial, and proverb comes from the Latin word proverbium, meaning “a common saying.” Proverbs are little stories or expressions that usually teach a lesson. You may have heard of the proverbial pot of gold at the end of the rainbow? Better to seek the proverbial penny saved, because that’s a penny earned. And the proverbial gift horse? Don’t look him in the mouth.