Setting the radius on a foliage asset does not prevent other foliage assets from being painted within that radius.
Regression (no) issues (does) occur in 4.10.4
Asset with radius will spawn with at least 500 units between copies of the asset, other foliage assets are unaffected.
Other assets can be placed near each other but must be at least 500 units from altered asset
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-30350 in the post.