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> If it has been crippled so that it can't run in reverse, that's crappy and unfortunate, but it makes it no less of a heat pump.

Yes, it pumps heat, but it's generally not referred to as a heat pump if it doesn't have a reversing valve and all the accoutrements that go with it (coil defrost heater, etc). I wouldn't say not having all those parts make it crippled, a refrigerator/freezer isn't crippled because it can't heat food, although some commercial units can be set to keep cold food cold or hot food hot because they have reversing valves.

If you have utility natural gas at reasonable prices, gas fired heat can be very economical, and it might not be forseable that you would ever use electricity for heating, in which case a reversing valve is a waste of capital.