Repo:
1. Open the profiler and capture a bunch of frames
2. Save the capture
3. Load the capture
4. use RawFrameDataAPI to loop over threads
eg:

int frameIndex = 0;
int threadIndex = 0;
const int maxFrames = 300;

while(frameIndex < maxFrames)
{

while(true)
{
using (RawFrameDataView frameData = ProfilerDriver.GetRawFrameDataView(frameIndex, threadIndex))
{

if (!frameData.valid)
break;

Debug.Log(frameData.threadId);

}
threadIndex++;
}
}

Expected: threadId is 0 only once for main thread
Actual: threadId always returns 0