Mathematically, I can accept that. But practical experience hasn't borne the same conclusion. One morning arriving at KDEN, dog-tired after a long night of flying, I settled into the routine of flying a visual approach, backed-up with the ILS, into our home airport. Captured the glideslope and decended on it, too tired to care about much of anything.
At about 10 DME things started to get my attention, as the farmfields I was idly gazing at were whizzing by rather close. A check of the radar altimeter showed less than 2000 feet. (1500? It's been awhile) My first officer had just noticed the same thing. We stopped the descent, recaptured the real G/S, and continued.
But this glideslope felt real. Solid as a rock, no flags, and produced the usual 750fpm rate of descent. It was just in the wrong place. Weird stuff happens.