I will post it again, though you can find it on post #94.
A Copious and Critical English-Latin Lexicon dixit:
OR, aut; vel; ve (enclitic): sive (or seu; rare in Cicero; common in poets and later prose writers). NB Aut stands in disjunctive sentences when one clause is entirely apposed to the other; vel when the opposition is only partial; ve is usually connected with single words, not with clauses, denoting reciprocal exclusion; sive, seu, or si, with vel, implies a difference merely in name or in the form of expression; e.g., audendum est aliquid universsi, aut omnia singulia patienda; de nostris rebus satis, vel etiam nimium multa; non sentiunt viri fortes in acie vulnera; vel, si sentiunt, se mori malunt; esse dico ea quae cerni tangive possunt; Minerva sive Tritonia. We may say that aut distinguishes, vel co-ordinates, sive denotes synonyms, ve is a milder vel. Aut distinguishes things and expressions which are diametrically opposed to each other, or, at least, are considered as widely different; vel implied that it is indifferent which of several things takes place, or which of several propositions is affirmed; it matters not whether they be different or alike; vel, for the most part, distinguishes only single words, more rarely whole clauses; and when it does so, it implied only a slight or nominal distinction: sive is used, (1) when, with reference to one and the same subject, a choice is given between several names and predicates; or, (2) when a speaker or writer, himself in doubt or suspense, leaves the choise with the hearer or reader …… Either - or, aut - aut; vel - vel; sive - sive; or seu - seu NB sive - sive usually with the indicative unless the sense requires a subjunctive.
And the reason why it cannot mean an either/or in the normative sense is that context would render such a interpretation inconsistent given the very following words it used for John 3:5 “as it is written”, the Caons on The Sacraments in General, Canons on Baptism, infallible statements of the past and the Church’s position on the matter since the patristic period, such as refusing to bury catechumens and distinguishing catechumens from the faithful by splitting the Mass in two (Mass of the Catechumens & Mass of the Faithful), etc…