Cloud Sync Engine cloud files search (SearchHandlerFactory) does not seem to work with Explorer

The cloud sync engine documentation is pretty clear on this: https://dori-uw-1.kuma-moon.com/en-us/windows/win32/cfapi/build-a-cloud-file-sync-engine#cloud-files-search

I should be able implement IStorageProviderSearchHandlerFactory (https://dori-uw-1.kuma-moon.com/en-us/uwp/api/windows.storage.provider.istorageprovidersearchhandlerfactory?view=winrt-26100) and have Windows Explorer do smarter things when searching my cloud sync engine.

However, what I am finding is that my COM class is never activated - I even used Process Monitor and saw no attempts to read the SearchHandlerFactory registry key.

Also, notably the documentation mentions OneDrive, which itself has a SearchHandlerFactory registered, but I also do not see it being activated or used.

Is this a known issue? Perhaps the documentation was aspirational but doesn't actually work (yet?)