Earlier quoted context omitted.
I didn't say they have atomic clocks. They do have clocks, though. Like most computers do. And they are high-precision, and are low-drift enough to predict the locations of satellites as long as they have been re-synchronized within the last few days or so. Which, as you say, also happens by just observing the time signatures from the satellites. You need four visible satellites to determine your own time, though, wh…
Your final point conflates icbms with cruise missiles - very different things. I don’t believe icbms use TERCOM or visual matching.
Nor they use GPS for that matter. ICBMs are completely inertial.