I agree it would be a very necessary feature. I often see that my active calory count for short bike rides is close to zero which is annoying. For example: cycling 5km to work in the morning gives me roughly 100 active calories when I track it. When I don't, it's around 10-20 (I guess because the heart rate sensor measures less accurately and frequently when no activity is started?).
Same request here.
Just moved from Fitbit where it would detect many types of activities automatically. Not sure why Garmin would only allow Running and Walking where "Move IQ" does a really good job at detecting I was on a bike so clearly detection is there and working well.