I disagree, anything historical you have the actual event as reference, you can cast anything that doesn't straight up give offense. Adapting a story based on fiction requires much greater attention to detail. Everyone knows D-day happened, there is no disbelief to suspend, in the realm of fiction it is a lot easier to be pulled out of the story specifically because it isn't real.
You see the same with characters, if you have a story based on a real person, it's ok for him to know 15 languages if the real person did, in a fictional story that will straight away take you out of the character if it isn't extremely well written.
If you are good at turning your brain off or simply don't have one that works very well to begin with I can see how nothing takes you out of a story though?