You're on the right track! If both Windows 10 and Windows 11 machines are connected to the same WiFi router, they're essentially sharing the available bandwidth provided by that connection. This means that the speed you experience on one device can affect or be affected by the usage on the other.
Keep in mind that WiFi 6 routers are designed to handle multiple devices more efficiently. They utilize features like OFDMA (Orthogonal Frequency Division Multiple Access) and MU-MIMO (Multi-User, Multiple Input, Multiple Output) which help manage concurrent data streams, but the total throughput of the internet connection is still a shared resource. So if one device is heavily using bandwidth or if multiple devices are active simultaneously, it can reduce the speeds available to each one.
Thus, while WiFi 6 helps in distributing resources better amongst connected devices, the overall speed might still be limited when all devices are actively drawing from the same connection. Let me know if you need more details or have any other questions!