It is, but heat pumps are evolving quickly to make this less of a concern.
Most existing gas furnaces are already very oversized for their ductwork. As you may have already noticed, when your gas heat comes on, you can hear it blowing out of the registers in some rooms. In many cases, you have existing gas furnaces pushing 2000 CFM through ducts that weren't really designed for it. But they needed that much airflow to get the heat out of the combustion chamber otherwise things other than the gas start to burn. Not great.
Because heat pumps (even at larger sizes) operate at lower outputs and with variable speed motors, they're already going to be pushing less air than your existing furnace, which is part of the reason heatpumps are quieter. What this means in practical terms is that even a larger sized heatpump that is near the max range of your ducts is:
a) still less than the airflow of your current gas furnace. b) able to intelligently ramp down most of the time well below that, only ramping up if needed to crank out some extra heat during those really cold temperatures.