Originally Posted by Adlerdriver

Your math is not correct.

To make them 1500' low following the older glide path, the threshold would have to be displaced almost 5 miles. How far are you usually away from the runway at 1500'? 3:1 usually gets you, say 5 miles, right?

Even at the extreme of the 750' threshold move you mention, following the old glideslope would only put them 40 feet low.