I don’t have hands on experience on it but they are probabling lying on the 50Hz GPS. There are no currently supported receivers that will do 50Hz, so either :
They are using EOL products (Venus838FLPx or Trimble MB-Two) with means they can’t produce a lot of them, and they are quite expensive as well
They are using massively expensive (Talking 300 USD or more) GPS module that can do up to 100hz.
They are using 25Hz (or even less precise) GPS modules and uses 6DOF IMU to interpolate the signal between GPS Fixes.