‘scholar’:
By your reasoning the opening words o Dan 1:1 clearly identify a 6th century BC historical setting
Huh?! Have you totally lost the plot? Your claim isn’t at all supported by ‘my reasoning’. The opening words of Daniel identity a setting, but there’s nothing about the statement that confirms when it was actually written. You don’t understand that a later writer could have access to historical details of an earlier period? What is wrong with you?