Are you using WPO for wind effects? You may need to enable evaluate WPO for raytracing (may incur significant performance costs)
That doesn’t apply to non raytraced shadows though.
For flat meshes like foliage you’ll want to bias the shadow pass downard in the direction of the vertex normal. This will make the shadow casting leaf geometry rest slightly below the actual mesh and unable to cast on the terminator line.
There is also an engine level cvar that can bias virtual shadow maps, but I don’t recommend using it because most meshes won’t need it.
Try using a higher poly version of the mesh to confirm if that solves it. For the purpose of testing, you can use the engines native modeling subdivision tool.