Satellite data is limited
You can see what is where, but you can't see how many people (and who) go there.
I speculated yesterday that maybe it could be Apple they're upset with. Looking at it from the point of view of a paranoid state (substitute China/Apple with US/Huawei for the mirror view) Let's say you have a secret military base. It is obvious on satellite so the "enemy" will know what buildings there are and can make some educated guesses as to what is going on there. But they would make better guesses if they knew there were 10 people a day showing up to work there versus 500, and even better guesses if the knew the identities of some of the people working there.
So imagine a Chinese employee working at such a secret military base. Because they have standard opsec, when he arrives at the main gate in the morning he checks in his personal cell phone, and it is put into a metal locker. When he leaves in the evening they give his phone back and he drives home.
If he's got an iPhone Apple isn't gathering any information about the secret base, they can't tell which building he works in and even if a paranoid state assumed Apple was bugging the phone to find out secrets it would do no good since it is sitting in the metal box. But despite that Apple could tell who works there, because the phone would know its location until the main gate then go offline for 8 or 9 hours, then re-appear at that main gate and drive home. So it is pretty obvious who works there, so if Apple either overtly cooperated with the CIA or the CIA had compromised Apple's internal systems (which a paranoid state would simply assume, because they're paranoid) then they'd know who he was, where he lived, what places he frequented in his spare time, etc. That information would enable a spy to know where to go to "just happen" to meet him and probe him to see if he would potentially turn and become a spy for the US. If he looks unlikely to turn, you have multiple options, maybe you get lucky with the 6th or maybe something changes about a guy you thought was solid (he loses a lot of money in investments, his kid can't get into the good school, whatever) and now there's a crack they can work to turn him into an asset.