Trying to implement an IThumbnailProvider, and came across this example:

https://github.com/microsoft/Windows-classic-samples/blob/main/Samples/CloudMirror/CloudMirror/ShellServices.cpp

Some questions:

1. AFAIK the behavior for detached std::threads when the program exits is unspecified (or UB? not sure); is this example depending on some Windows implementation detail? Would the class object eventually be properly revoked in this case? Does it have anything to do with the If the caller resides in a single-thread apartment, CoWaitForMultipleHandles enters the COM modal loop, and the thread's message loop will continue to dispatch messages using the thread's message filter. in CoWaitForMultipleHandles‘s docs?
2. Why COWAIT_DISPATCH_CALLS if it only works in Application STA? Does it mean that in this case it’s equivalent to COWAIT_DEFAULT?