It does not. It reduces speedo reading by 4%, which makes it more accurate. I have researched differences in (initial) outer diameters among several popular brands, and the math says you shouldn't be out more than 1 mph at sub light speeds.
I encourage you to carefully check your own speedo error. First check your tire pressure. Then set your speedo to KPH. Download an app that logs peak speed to at least 1 decimal. I used "GPS HUD Speedometer free" from AscendApps (not affiliated) also set to KPH, with 1st decimal precision.
Pick a speed, as fast as you are comfortable doing in your area. Maintain that speed carefully for a few seconds. Divide by GPS peak indicated. Repeat a couple times and average your results.
I'd love to hear what you find, as well as what is your tire model and miles since your last rear tire change.
Thou Shalt Respect Thy 10, And Revel In It's Power, For It Is Good, And Plentiful.