Hi
In addition to up to 10 apps that you can choose to add to the Dock permanently, it is normal for Recent and the Now Playing app to also be shown automatically, as and when appropriate - and they cannot be removed in the same way as apps that you have added to the Dock.
For apps that have not yet been added to the Dock permanently:
- Recent automatically shows the app that you used most recently.
- Now Playing is shown automatically when you watch or listen to media on your Apple Watch or iPhone, including music.
If you have not yet reached the limit of 10 apps, Recent and Now Playing also show the option to Keep in Dock, which, when tapped on, adds that app to the Dock permanently.
More information:
Switch between apps using the Dock on your Apple Watch - Apple Support