It's not him who came up with this. There's one such body kit sold at Amazon for ages and the other one (that one even has wireless charging) is sold on Aliexpress for like $15.
Released in 2015, the Apple Magic Mouse 2nd Gen has had a surprisingly enduring life. It is still in circulation, with Apple bundling it with the latest M3 iMac. But its design makes it barely usable in some instances, and a design hacker has just fixed the mouse's biggest weakness.