RobboRider,
Your post very nicely states the concern!
I have worked several flight tests of GPS systems, and it seems that the rotor modulation treatment within the receivers works very well. Generally, there is more issue with banking and its influence on the antenna's ability to see satillites on the horizon. There are times when the gps will drop below proper satellite geometry when in a bank, yet be very healthy in level flight.
It seems that the way gps is being handled depends on whose government built it. The idea expressed in the CAA paper that it is unsafe to depend on it is extreme, to say the least, as is the idea that RAIM is not conservative enough. Curiouser and curiouser.