I am not disagreeing, but for the unlearned what does John 3:3 really say?
John uses the word "from above" (anothen), not "again". The word anothen means also "from the beginning." Nowehere in the NT does it mean "again." The word for "again" in Greek is palin. Curiously, Paul uses the phrase plain anothen once in the entire NT, which translations treat as simple "again". But anothen alone is never translated as "again" except in John 3:3, and that only by some Bible versions, not all.
Judging from the Nicodemus' reaction (John 3:4), he (mis)understood Jesus' words to mean literally "again". The problem with that is that Jesus and Nicodmeus would have been speaking in Aramaic, not Greek, and such misunderstanding, while very remotely possible in Greek (based on Paul's singular example), is not possible is Aramaic.
Bible scholars conclude, therefore, that the conversation never took place, but was rather created by John for a specific agenda.