Very interesting PVC !

IIRC the legionaries advanced shoulders to shoulders much like a phalanx, unlike the much more spaced formation they normally used, forming a shield wall that was used against the arrow volley of the barbarians (probably to show an image of something like a "Tortoise" that everybody knows about roman legionaries)

And you are so right, the romans even let the barbarians charge them instead of throwing their pilla and then charging in.

The Roman General even had his cavalry charging through the woods having a dog acompagnying him