And it’s not just the finish, is it. Barbour jackets are distinctive in other ways, like the collar and pockets. They’re typically hip to thigh length too, whereas George’s coat would’ve hung much lower, probably to the knees. The effect that running or even walking at pace has on such a garment would imo be highly noticeable.
Wool coats typically shed a lot of fibres too, yet none matching George’s coat were found at the scene. People typically retort to this by saying the paramedics destroyed the scene, yet the prosecution were happy to introduce fibre evidence when it suited them - no matter how weak that was. Heads we win, tails you lose.