RealityKit Custom ARAnchor not syncing across devices

I’m using Apple’s custom ARAnchor in a config.isCollaborationEnabled = true environment.

When I call the following on DeviceA:

let boardAnchor = BoardAnchor(transform: last.worldTransform, size: CGSize(width: 10, height: 11))
arView.session.add(anchor: boardAnchor)

I can see the delegate func session(_ session: ARSession, didAdd anchors: [ARAnchor]) get called with the BoardAnchor on DeviceA.

However, DeviceB does not receive such a delegate call.

If however I add a non-subclassed ARAnchor on DeviceA, I can see the delegate called on DeviceB.

let namedAnchor = ARAnchor(name: "test", transform: last.worldTransform)
arView.session.add(anchor: namedAnchor)

So I’m really confused as to why the subclass doesn’t work…any ideas?

class BoardAnchor: ARAnchor {
let size: CGSize

init(transform: float4x4, size: CGSize) {
    self.size = size
    super.init(name: "Board", transform: transform)
}

override class var supportsSecureCoding: Bool {
    return true
}

required init?(coder aDecoder: NSCoder) {
    self.size = aDecoder.decodeCGSize(forKey: "size")
    super.init(coder: aDecoder)
}

// this is guaranteed to be called with something of the same class
required init(anchor: ARAnchor) {
    let other = anchor as! BoardAnchor
    self.size = other.size
    super.init(anchor: other)
}

override func encode(with aCoder: NSCoder) {
    super.encode(with: aCoder)
    aCoder.encode(size, forKey: "size")
}
}

Delegate

func session(_ session: ARSession, didAdd anchors: [ARAnchor]) {
    
    for anchor in anchors {
        DLog("didAdd anchor: (anchor)")
      
      if anchor.name == "test" {
        // Non-sublcass ARAnchor ok
      }
      
      if let board = anchor as? BoardAnchor {
        // Never called
      }

    }
  
}