So, a motorbike a passes a human powered vehicle? That should come as no surprise to neither of you. :)
To be honest, I don't get the appeal of e-bikes for the type of riding you do. Getting up to 15 MPH when you're riding for 8 km in a city when stopping for lights should be no problem without disabilities on a decent bike. An 8 km ride takes 20 minutes at 15 MPH. At 20 MPH it's 15 minutes. You'd add 5 minutes off your ride and get some proper exercise.
As a reference, my grandmother rode her bike 12 miles to school and then back at the age of 10.
E-bikes make a lot of sense for longer rides with cargo bikes packed kids, trash, food and whatnot.