Well, I figured out the answer to my own question. The vendor who installed my furnace did not set it up properly.
If your G71MPP furnace flashes a code starting with capital "H", then it is not configured properly and it is running in two-stage mode.
If your furnace flashes a code starting with lowercase "h", then it is properly running in variable mode.
Similar to the other thread, the #2 dip switch had to be flipped up (or on) to put it in variable mode. The dip switch is very small and on the left side of the board behind the bottom furnace panel.
It's unfortunate that these furnace vendors are not setting up the G71MPPs properly, especially since we are paying several hundred dollars more for the variable speed functionality.
Finally, so far I've only noticed levels of:
"h40A###"
"h70A###"
"h80A###"
"h100A###"
So, I haven't been impressed with the furnace itself and the variability of the stages. It may have been better to just stick with the two-stage model for less money.
I hope this thread helps others.