I think Zwift just adds speed to a group of riders. Once there are 3 or 4, speed goes up even if the same two riders stay on the front.
I just wish Zwift would work out the proper drafting algorithm. That is how the draft should work
I remember riding in a group at the Lincoln 100 Grand Prix. There was a 15mile section
https://www.strava.com/activities/1567074434/analysis/51/4632
There were 15 of us, 3 or 4 strong lads pulling the pack into a headwind mostly. I was sat in 3rd or 4th row and was travelling along at 21mph in Z2 at 130bpm. You can see a bump in my HR, that is where I did a 5 min stint on the front, my HR jumped to 170bpm
View attachment 538054