I’ve written more or less the same thing about this movie before on this board. It was a fun little movie. I’ve only watched it a couple of times, but I like it.
I think all of the historical inaccuracies were deliberate. I saw the movie quite a while ago, but I seem to remember a few scenes where period music blended to modern, and a few where archaic formal speech patterns faded into modern casual ones. The movie was trying to make a point about how the people of the time thought and felt about things by relating everything to modern equivalents.
Logos are modern heraldic symbols. Instead of a lion rampant facing a unicorn passant on shield pale crimson and gold (totally made up heraldry, by the way) they have a Nike swoosh on the armor. They knew exactly what they were doing there.
Some of the spectacular stuff that is historically accurate wouldn’t work in a movie like that. Ironically, modern audiences wouldn’t buy it. Argent’s fantastic-looking but historical helms would be way too elaborate for people to believe they were real. When you’re pushing suspension of disbelief in one way, you sometimes find that they’re resistant to accepting small details that may actually be real, but do not quite fit with what they believe to be true.
Romeo + Juliet did a similar treatment, keeping the original language, but making the settings and costumes thoroughly modern in an over-the-top action film kind of way. Let’s face it, Shakespeare would have been closer to Michael Bay crossed with Spielberg than Hitchcock or Welles. He didn’t consider a fight scene to be very good unless the first few rows were covered in pig’s blood by the end of it.