Yes that is true. I just read it in the pdf file I have for the extender. It states:
Without a valid GPS signal, the Network Extender cannot function
properly, and calls will be redirected to the nearest compatible
This is what it says about the GPS light along with the system light:
GPS LED:should be a continuous blue light,indicating that the
Network Extender has locked onto a valid GPS signal. If the GPS LED is solid red, the internal antenna may not be able to detect a GPS signal and installation of the external GPS antenna might be necessary. If the GPS LED is persistent magenta while the System LED is slow-blinking red, this indicates a failure condition.
I have attached the pdf in case you might want it, if you don't already.--
Long you live and high you fly, and smiles you'll give and tears you'll cry,
and all you touch and all you see, is all your life will ever be.