Exercise ring too easy to close

This document explains, how the Exercise goal is credited by the Activity.app - see paragraph 2:

https://support.apple.com/en-us/HT207941

To make sure that you earn Exercise credit during walks, allow the arm with your Apple Watch to swing naturally. For example, while walking your pet, let the arm with your watch swing freely while the other holds the leash.

If you need both hands while walking, for example to push a stroller, you can still earn Exercise credit with the Workout app. Open the app on your Apple Watch and tap Outdoor Walk. The Activity app relies on arm motion and an accelerometer to track movement, but the Workout app can use the accelerometer, the heart rate sensor, and GPS.

My wife and I spent a lot of this weekend walking around. Hand-in-hand.

Did you run an outdoor walk workout while walking around?

If not, the Activity application will count the exercise based on the motion sensor and it will depend on the motion of your hands. For example, if you are wearing the watch on your left hand and you could swing the left hand freely and naturally, while you were holding the left hand of your wife, so her left hand could not swing freely, your watch may have registered more exercise than hers.

My watch is registering a lot more exercise, when I am can let the arm with the watch swing freely than when I am keeping my hands in the pockets.

See Calibrating your Apple Watch Series 1 or earlier for improved Workout and Activity accuracy - Apple Support

Calories burned is dependent on many factors including body weight, heart rate and others. Different people will have different amounts of calories burned for what seems to be the same activity.