Historical accuracy - "Saul Fia" & "The Grey Zone"

Both are outstanding films, but they are still flawed in different ways, I think.

Let's have the highest standards of historical accuracy.

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"The Grey Zone" was more accurate in its production design.
The crematoria II and III looked nearly exactly like the historical ones.
At least from the outside and according to the plans.
Even the location within the Auschwitz-Birkenau complex was correct.

In "Son of Saul" the production design and locations sometimes don't look accurate.
It's more like 'important sites' of the camp closer together than they were.
There is a mistake f.e. right at the beginning:
The trains were not as close to the gas chambers.
And the victims would have walked a different way,
not from the woods to the trains to the crematoria III and IV.
That's impossible according to the Auschwitz-Birkenau plans.

"Son of Saul" is of course much more accurate in terms of languages spoken.
That was a major flaw of "The Grey Zone".

And the costumes of the Sonderkommandos seem to be more accurate.

The actors look in "Son of Saul" more like the real-life ones, f.e. Nyiszli.
The casting was more off in "The Grey Zone".
In "The Grey Zone" 'Miklos Nyiszli' didn't look like the historical Nyiszli.
'Josef Mengele' didn't look at all like Mengele.
'Erich Mußfeldt' (Harvey Keitel) didn't look at all like Mußfeldt.

Actually Harvey Keitel was much too old for his character:
He was about 61 years old, when they shot that film.
Mußfeldt was executed in 1948, when he was only 34 years old…
While in Auschwitz-Birkenau he was in his late 20s.
An SS commander in Auschwitz-Birkenau in his 60s, like Keitel
would have been impossible.
They were nearly all young men.

A critic said about "The Grey Zone" that the actors look "too well fed",
but that's probably a false criticism:
The Sonderkommandos never suffered real hunger, because they could eat what they found in the victims' pockets.
And they got food, alcohol and tobacco.
But how much did they get ?

In "The Grey Zone" they show massive quantities of food and alcohol.
I guess because Nyiszli described this in his book.
But Nyiszli did exaggerate sometimes.

In Martin Amis' novel "The Zone of Interest" they get much less food,
a little more than prisoners.
(Amis claims to have done intense research, but I have doubts.)
How much food did they really get?
Does anybody have a reliable source?

The biggest mistake in "The Grey Zone" was in the text at the end:
The Sonderkommando revolt was not as successful as it says.
They only did destroy one crematoria, not two.

In "Son of Saul" there is a boy who survives the gas chamber.
There is, as far as I know, no document that something like that happened, is there?
I only know that Miklos Nyiszli wrote in his book, that a girl survived one time,
but was killed later.
In "Son of Saul" the character Nyiszli actually refers to such an event.
So it happened more than once?
Did a boy ever survive the gas or did the filmmakers made the boy up?

And there's something about "Son of Saul" that was odd:
The main character Saul has no big problems switching between different commandos.
By doing so, the filmmakers can use him as our guide through the camp, but would it have been possible for someone in the Sonderkommando to change his 'work' like that ?
Didn't they always have the same task ?

And last but not least: In "Saul Fia" it says in the text at the beginning that "all were killed after a few months".
That's true in general, but we know that some Sonderkommando could survive much longer, even years.
Filip Müller for example.

Other comments?
Does anybody know more?

Thanks.