> 2. They had future plans for the mic, but it was disabled, so it wasn't mentioned by the marketing department
If you design in something which is later not used, you don't populate that part of the circuit board. Not unless you're intending to use it later, anyway. Components cost money.
A software equivalent would be "we had plans to offer an integrated backup system but that didn't happen, although we still upload your contacts list and the contents of your SMSes to our servers."
You can add hardware features in order to support features you want to support in the future, but not advertise them in case those features for some reason don't come to fruition. If they had advertised "contains a microphone" there could be users who claim false advertising if they can't use the microphone. It's stupid but I can see a lawyer making the argument.
As long as the microphone never recorded anything, they're no legal downside to including it and not documenting it. There could be a slim but potential issue with advertising a microphone that the customer can never use.
The response to this incident is showing that that view is changing though.
An extra co-processor or something, sure. A device which the capacity to invade the user's privacy and/or compromise their security? Not so much. It'd be like having a 3G connection hidden in a security camera and not telling anyone.
Tesla has a suite of sensors installed that are not currently used because they intend to solve the self-driving car problem with them in the not-too-distant future.
Nintendo released multiple generations of consoles in the US with expansion ports for peripherals that ended up not making market sense to bring to the US.
If you design in something which is later not used, you don't populate that part of the circuit board. Not unless you're intending to use it later, anyway. Components cost money.
A software equivalent would be "we had plans to offer an integrated backup system but that didn't happen, although we still upload your contacts list and the contents of your SMSes to our servers."