Now that Icon is in charge maybe they won't screw it up.
Iconic bought a majority of the Beach Boys; the Brian doc is not under the purview of the group or Brother.
I would imagine one if not several outside production companies funded this Brian documentary, with an eventual distributor paying for distribution rights. Those are the parties making decisions.
While one would think/hope/assume Iconic, now essentially running the Beach Boys, would make some attempts to coordinate with concurrent solo projects, especially a bigger one like a feature-length Brian doc, ultimately I don't think this doc is running through Iconic in any way.