Disable selection of root branches while having multiple=false

[s3dse]

Hello,

I have a tree that should allow only a single selection. The root branches should not be selectable, while their children branches and leafs should be selectable. Settings disable-branch-nodes is not an option.
I set isDisabled=true on the root nodes and set :flat="true" on the component. However, I need the tree to only allow a single selection. I get a warning if I set :multiple="false" on the component, just as the documentation describes.

Is there a better way to do this, without receiving a warning?