Sounds like a good idea.
however note that the sun is only straight up on the equator
Plants tend to grow towards the sun. That would likely mean different angles based on which side of the eqator is getting more light during the sprout season of the plant. (Talking about small plants more than trees).
Realistically, if you align to surface normals you can usually barely tell the difference or notice it not looking as “natural”. Particulalry, if the plants aren’t static and move with wind displacement, their starting angle barely matters at all.
Obviously to an extent. If you have 2km with just 1 plant to look at, yes. You would probably be able to say… it looks off. ;p