I get what they were going for: force the user to use it as intended because the battery really lasted long enough for most people. Otherwise people would just have left it plugged always, and the cable+port would have needed different mechanical strength. But that really annoys anyone who would have left it charging if not most of the time. I think it would have been a better experience by leveraging software instead: detect that it is close to the end of the day and battery is low, and notify the user thwt they need to charge it when they stop using it, if leaving the underside port, or use notifications to annoy people into disconnecting the mouse when fully charged, if the port was moved to the obvious place. You're still annoying people, but you're less likely to end up with an unusable belly up mouse midway through your day.