How to use app previews in the dock with VoiceOver?

watchOS & Apple Watch Apps

In watchOS 2, there was a function called „Checks“. Since watchOS 3, they replaced the „checks“ by the Control Center. Now, the short previews of apps should be available via the new dock but VoiceOver is only telling the app names. My question is now: How can I use this short app previews with VoiceOver?