My Button Registers Twice When I Only Press It Once

You are right that nobody writes about this, and you are right about the cause. It has a name: contact bounce, or switch chatter.

A button is meant to make one clean electrical connection when pressed. As the contact surface degrades, the connection stutters during the press, making and breaking a few times in a handful of milliseconds. Game code and browsers both have debounce logic to swallow that, but it is tuned for a few milliseconds, and once the bounce stretches past that window the second make reads as a genuine second press. Seven times in ten is well past the point where any amount of software filtering will save it.

The reason this gets confused with other faults is that it is intermittent by nature, and people often blame the game first. Your test result settles it: two distinct press events from one physical tap, on one specific button, is contact bounce and nothing else. Firmware does not cause it, and no deadzone or sensitivity setting touches it.

Cleaning the contact is worth one attempt because oxidation and residue make bounce worse, and on a pad under a year old there is a reasonable chance the surface itself is fine. If it returns, the fix is replacing the contact membrane or, on controllers with discrete microswitches, the switch itself. At 11 months you are also inside warranty on most purchases, and this is an easy fault to demonstrate to a retailer, because you can show them the double press on screen in a browser in about five seconds.