Fitness app not syncing with the iPhone when I do not wear the Watch

Hello. I have a watch 7 and an iPhone 12. When I do not wear the watch the fitness app shows no activity forcing me to wear the watch all the time.

Is there any way around it?

Like picking up the activity from the item (watch or phone) that is moving with me?

Or is there a way to make the iPhone the main device?

Or a way to manually switch back and forth.

There are times I do not want to wear the watch.

Thanks