Totally agree. The "heroes on both sides" line in particular tells us nothing and is arguably nonsensical. I suspect you're supposed to assume Grievous (appearing with no explanation out of nowhere) is one of these "heroes," but to whom is he a hero? We're never shown the Separatist side of things from the perspective of anyone who would be in a position to consider anyone heroic on that side. It's just such a weird, weird piece of writing, even for the prequels.