Yeah, sometimes there is a disconnect between the brain and the fingers...
What it should have said is the propagation VELOCITY is about 250 meters per microsecond or 4 nanoseconds per meter.
For those interested, the device I ordered is: https://www.ebay.com/itm/174136333219
Note that one needs to specify which GNSS system(s) (max of two) you want to use. As I am in the US, I chose GPS+GLONASS.
Re the Adafruit GPS HAT: I recently upgraded my old GPS HAT to the current GNSS HAT. It is too soon to have precise numbers, but it appears that the accuracy of this HAT, to a 95% confidence level, is a bit under 200 microseconds.