Does an Apple TV stream 4K movies if the Internet connection is somewhat less than the recommended 25Mbps?
Yes, you can stream 4k movies on the Apple TV 4k with a somewhat less than the recommended 25 Mbps internet connection.

In practice the available bandwidth for streaming the movie should not drop 15 Mbps to ensure 4k streaming. So real life experience depends a lot on what else you're using your 22 Mbps internet connection for at the same time.

How exactly the streaming quality is determined depends on the app you're using to view the movie. For example Netflix allows you to lock the quality setting to High, but you might experience lots of waits for rebuffering during the movie, if your internet connection is too slow.

If the movie is streamed from the iTunes Movies and TV Shows app, you can adjust the quality in the general AppleTV settings in the menu Settings > Apps > iTunes Movies and TV Shows.

From this menu you can disable "QuickStart". This means that you'll have a wait before the movie starts playing, but it will display in the best available quality even on a slow internet connection.