Forum:KB:On canonicity of Battlefront

Wasn't able to find this elsewhere, other input would be appreciated.

How canonically accepted is the story of the 501st Legion in Battlefront II?

The primary reason I bring this up is the cutscene following the story mission on Felucia. The narrator states that Secura praises the troops fighting alongside her as they were being shipped out, then recounts that they were grateful for the helmets they wore as they would have been unable to meet her gaze.

This could be interpreted as guilt from foreknowledge of Order 66's execution, but since it's been stated that the order was not preprogrammed it does make me wonder if the storyline there is generally accepted as valid.