As I've stated in another thread, Frank Bradbeer used to tell me many stories about the days of GDB, and why Maurice Grant followed the path he did. I avidly consumed all this information, and I still prefer the tingle and fizz of an organ from that era.
One of Maurice's justifications for low wind pressures was that, although air is a compressible gas, at low pressures it acts more like a liquid. Therefore the movement of air through the pallet hole, through the (open) toe of the pipe to the flue would be almost instantaneous, or at least much faster than high pressure wind having to wor