It seems to me that George Miller agrees with the fan belief that the Mad Max films are a series of tales rather than a chronology or anything like that, because there are some huge discontinuities, and I am fairly sure that is intentional. You may dispute this, but you will have to come up with some convoluted explanations for at least some of these points:
Some of the big ones:
- “Shiny” and “chrome” are never said once in Furiosa.
- One of Immortan Joe’s sons is different in each film, although Rictus is in both. There is no mention of a third brother in either film.
- There is a history woman in Fury Road and not a history man
- In Fury Road, the false-nosed man is the head of Gastown and not very interested in helping Immortan Joe even though he does it out of fealty.
- In Fury Road, the titular road is implied to be the road to The Green Place. In Furiosa, it’s the road from The Citadel to Gastown.
- In Fury Road, Max had clearly never seen The Citadel before until he ran out of the cave and saw where he was. In Furiosa, he is within view of it in his Interceptor.
- There’s no suggestion that Gastown and The Bullet Farm had their own horde of drivers in Fury Road.
- Furiosa is told by her mother in Furiosa to use the stars to get back to The Green Place, but in Fury Road, she just goes east. And during the day.
- In Furiosa, the Warboys worship at the pile of steering wheels. In Fury Road, they take the wheels for their cars one by one and choosing which wheel is a ritual thing.
The biggest one, though, is that Furiosa ends where Fury Road begins, at least that’s what the film seems to show, but Gastown and The Bullet Farm are rebuilt and restaffed enough that runs are possible again, and Immortan Joe’s army is much bigger and more powerful.
I’m not complaining at all, I think it’s fascinating. The idea of a film universe as folklore rather than “fact.”
Incidentally, neither film ever explains why Furiosa has an American accent.
She didn't have to be there for the tree to grow. And we don't even know if that happened because even the history man said it was just one story.
True she didn't have to be there but we were shown her picking the first fruit from the tree and then it cuts to the escape with the wives. Regardless of the tree though, the age difference explains the necessary time jump from Furiosa killing/catching Dementus to Furiosa making the Fury Road run.