I noticed this (stupidity/error) too. The only hedges that are knee or hip high are modern decorative hedges. The typical English or European hedge is from solar plexus level to over your head. English country hedges are often more like low bocage. It's pretty much the same in the Normandy region.
Excellent concealment/LOS blockers, but poor cover. Unless they are on buillt up embankments. (1-4 ft high and 2-6 ft wide of dirt)
What did you base your hedge research on Battlefront?
Nigel Steel