my 2015 always defaults to the screen that was last up, usually the radio station I or my wife were last tuned into. Have you set up your key? I think what you're looking for starts at the 1:10 point of this video. https://youtu.be/rjwp3fPSRjc Last climate control setting is also included in the saved information. Hope this helps.
That being said, if the radio is turned off, it'll default to the map screen :-|I kept forgetting to check this over the weekend, so I went out to mine just now at work and started it up. The screen was on the XM station I had tuned to while I was driving in to work this morning. That'd be annoying if they changed it so that the map/nav screen ALWAYS pops up by default on the newer models. Or perhaps it is just a setting that was already adjusted when I purchased this. I'm not sure it has much to do with the link posted, that was more to just adjust seat/mirror/wheel settings to a specific key fob. I didn't see that they reference what screen is on your infotainment system when you start your car. But they may be it, as I had done as the video instructed and synced the fob that I always use to seat setting 1, and did the same for the other fob for seat setting 2 for my wife (although often we'll still use fob 1 for everything, then she just pushes 2 to move things to hear liking once running).
2017 QX60 - key fob doesn't make a difference. The music will pick up when you turn it on, but it defaults to the map screen regardless of where you had it before. This is totally different behavior than my 2014 model, which would default to the last screen it was on when you turned the vehicle off.