What you are doing is, I guess, a type of base training.
This is where you do low intensity rides for a specific time per day.
What it does is builds your endurance (though ideally you should be doing longer and longer rides if it was actual base training).

You are not developing speed or anaerobic fitness, but base training - particularly if, over weeks, you make the rides longer - gives you an excellent endurance base.

The other way you could look at these rides is "transition" where you maintain a fitness level, but you still have your "training" ahead of you for specific rides (whatever those rides might be)

However, taking that "training" helmet off, any riding is good for you, because you are moving, keeping your heart busy and your muscles moving.