DisplayTask::SetSignal not firing

Question

Running the sample application for Windows.Devices.Display.Core & using a head mounted display (tweaked to make it look for specialised displays) I am able to present images to my monitor. But I am failing to get feedback on the presentation timing when using DisplayTask::SetSignal. Creating a DisplayFence by creating a dx 11 or dx12 fence, exporting it and then creating a DisplayFence with it, then passing it to SetSignal and calling GetCompletedValue or waiting on an event - the fence value never changes. Win11 24H2, no errors, tested on multiple Nvidia GPUs and driver versions