The GPS system is entirely passive. You don't 'probe' anything, rather you read a data stream broadcast from multiple satellites in the constellation and compute the location. All GPS access is 'local' and one way, from the satellite, to the receiver.
What China is doing is not being reliant on the US GPS system in case the US decides to turn full encryption back on. They're not the only or even the first to do this: the European Galileo system was the first global positioning satellite system after the US GPS, and it was created for the same reasons.