It can't be declared "accurate lore" because it doesn't appear anywhere in any of the games and has not been word-of-god confirmed like their ovoviviparity has. Those last two points you making are based on nothing at all.
Actually, it's based on character dialogs. One Argonian in Morrowind talks briefly about the tree-licking ceremony and its place as a coming-of-age ritual that could be literal, figurative or both, but doesn't go into detail with its relation to the Hist aside from the fact that there is one. Modryn Oreyn and others comment that licking the Hist sap is something argonians do. Someone on TIL once gathered a bunch of the various dialogs and in-game books information on Argonians.
Ah, found it copied out http://z8.invisionfree.com/People_of_the_Beasts/index.php?showtopic=10 Good thing too, as the original is missing.
And again with the word of god thing. We are permitted to do simple math with the information present, or were last time I looked. Seriously, the worst that happens if we take multiple circumstancial items together and assume what they loosely indicate is true, the worst thing that can possibly happen is that we're wrong about a species that does not exist being able to swap out six organs. Whoop dee [censored] doo.