Zwift and Strava mileages differ

I am finding that the mileage on Zwift is always 0.1-0.2 miles more than what gets shown on Strava. Any ideas why?  I am using Kickr…

That’s no surprise, it’s the same for real life rides too.

My Garmin always shows 0.1-2 miles more, same for average speed too.

According to Strava they are right and it’s the rest of the world that is wrong.