I’m not convinced this change does what’s intended, at least not in Build 19042.928.
The test is fairly basic: if you set up multiple file choosers with different starting points with SetDefaultFolder being called, the first default path set will be the one used for any subsequent file chooser. Debugging in OnFolderChanging does catch the switch up…
As per the MSDN for SetDefaultFolder - https://docs.microsoft.com/en-us/previous-versions/bb775692(v=vs.85):
Sets the folder used as a default if there is not a recently used folder value available.
So, I’m not sure SetDefaultFolder is what’s needed here. For me, SetFolder (what was there before) does actually set the desired starting folder, regardless if a default one has been set.