I'm an IT guy not a electronics guy; so I don't dare to say you are wrong
Good because I am a hardware guy.
but the info you provide is seem conflicting to me with other info available.
This means you are not understanding the other information correctly.
I don't know what you mean with equivalent.
It means 'the same as'
These requirements seem tight to me
They are not, remember you are not a 'electronics guy'
Arduino explicitly states that Vin does not go over the regulator
No you are wrong, no such thing is stated, the current from the Vin flows through the regulator.