I thought it had "full win32" support, ie, you can run win32 apps but they have to be modified. It's clear as mud though, MS says one thing but their windows store migration guide says another. The existence of the migration guide is rather telling though.
Desktop Bridge (Centennial) apps are modified to use the same appx packaging and installer format used by UWP apps. Unlike true UWAs they run with user privileges, not inside an app container, and so they have the same filesystem access as the user.
They can be distributed through the store but the onboarding process is much more arduous than with true UWAs (for which the Store acceptance process is largely automated since they're relying on the app container for security). AIUI to submit an unsandboxed app they expect you to already be an established developer and submit a request, wait for them to do a bunch of manual investigation of who you are and get back to you, etc.