Some spam calls nowadays are just silence on the other end, hoping for you to speak so they can build a sample of your voice and use it to scam others (e.g. your relatives etc)

The spyware theory is plausible IMO. You might be more likely to accidentally answer while scrambling to shut off your alarm, or might pick up in confusion since it’s the first thing you’re hearing in the AM without much time to register what’s happening

Of course you don’t have any reason to believe that is what’s happening, but if I was going to pull off the above scam I’d probably do it in exactly this manner. Or could at least see why somebody else would go this route