[mikeash]

Poor debouncing could conceivably cause a single push to register as two, or vice versa, but it's not going to cause a push to fail to register at all, which is part of every complaint I've heard so far.

I also see no reason that debouncing would require calibration. Basic debouncing just ignores any additional events that occur within a set period. That would just be set at the factory. There's a huge gulf between the timeframe of multiple events occurring due to switch mechanicals and the timeframe of legitimate ones.

Finally, the idea that somehow the Calculator app triggers a secret magic calibration step is just absurd. Even if you can somehow swallow the idea of software calibration of a simple mechanical switch, that detail makes it clear that this is nonsense.