StorageFile.CreateStreamedFileAsync throws wrong thread exception

Describe the bug

var storageFile = await StorageFile.CreateStreamedFileAsync("test.png", OnStorageFileNeeded, null)

throws a COMException with is claiming to be on the wrong thread. This is happening for me on the UI thread, which I think should work and has worked in WinUI 2. (I have some difficulty in providing more information, as for me VisualStudio 2019 16.10 Preview 2.1 becomes completely unresponsive when this exception is encountered. Restarting explorer.exe enabled me to recover from this exception.)

Expected behavior Should not throw exception, this was working in UWP / WinUI 2.

Version Info

NuGet package version: WinUI 3 - Project Reunion 0.5: 0.5.5

Windows app type:

UWP	Win32
	Yes

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
October 2020 Update (19042)	Yes
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

[Marv51]

This seems to be working now 🥳

[manodasanW]

I believe this is the same issue as https://github.com/microsoft/CsWinRT/issues/612 . I am able to repro to this issue and should able to confirm whether my fix resolves it or not once I am done.