UDM SE caps out at about 600 Mbps with 100% CPU load?

Currently trying to figure out why I do not get the 1 Gbps in any download while the daily speedtest often reaches 950 Mbps+. Currently I have a script running that downloads from multiple speedtest hosters in parallel. Capped at ~600 Mbps. Then I tried this script on multiple clients. Still ~600 Mbps. Then I added Steam, Battle.net, EA, PlayStation and other downloads. Still ~600 Mbps. I finally thought about the console's hardware and well… 100% CPU load all the time. What the hack? This console is designed to handle 1000+ clients with 3.5 Gbps ISP throughput based on the Datasheet on the Ubiquiti Store.

So my question now is, what did I miss? Why do I even run in CPU limitations of the UDM?