What is said is the current capabilities. All other GNS systems have the same capabilities (though European GNS Galileo has some more modern features and the Soviet one is a bit of a shitshow)
The NTRIP RTK services we use just provides assistance for GPS+GLONASS, no Galileo or BeiDou. GLONASS is crucial because the satellite orbits are more visible at high latitudes providing better reception. Still, RTK should help cope with this problem but I might have to check last week's collections.