Ummm.... and? This is news?
And the reason Stripe gives for it is actually valid: to detect anomalous behavior and improve security.
It is readily apparent when a computer is operating a mouse (a script) or a human being. If your mouse jumps directly to the Buy button, and goes through the purchase process in a direct and quick manner, that's a pretty good sign there is no person running the mouse.
If they then compare that activity with your last 5 purchases, and geo-locate those purchases, they can quickly - in the time it takes to run a credit card - make a judgement that it is highly likely the individual's card or other credentials have been stolen, and are being used in a felonious manner.
I had friends that worked in credit card fraud prevention and the shit they know about humans and our use of technology is seriously amazing. They catch fraud SO fast nowadays... because of stuff like this.
If the author is so hacked off at their mouse movements being tracked on a site with a Stripe payment processor... I'd like them to present a clear use case for that data that impinges on the user's privacy, safety, or rights. Because I can't think of one.