PerfomAll() doesn't run TrackObjectRequests in parallel:

I see a linear slow down as more trackers are added in the loop below. According to the WWDC video I was hoping that performAll run all these request in parallel, but apparently not for TrackObjectRequest....

#if DEBUG
print("Frame processor: \(requests.count) tracking requests")
var observationCount: Int = 0
let trackingStart = Date()
#endif
for await observation in handler.performAll(requests) {
    if case .trackObject(let request, let trackedBlock) = observation {
        
        #if DEBUG
        observationCount += 1
        #endif
        
        guard let trackedBlock = trackedBlock,
                trackedBlock.confidence <= FrameProcessingThresholds.blockTrackedConfidenceThreshold else {
            // lost track of the block, remove the tracker
            blockTrackers.removeValue(forKey: request)
            continue
        }
        
        trackedBlocks[blockTrackers[request]!] = trackedBlock.boundingBox
    }
}

#if DEBUG
print("Frame processor: \(observationCount) observations")
print("Frame processor: tracker took \(Date().timeIntervalSince(trackingStart)) seconds")
#endif