yes they can still sense heat, just like i can with the back of my hand. But they can no longer sense which direction the heat is coming from. If you have a pit, and a source of warmth in front of you, some areas in the pit will get infrared radiation and other areas of the pit are in the shadow.
..........
<--- two heat sources (please ignore the points ....... couldnt get it done without them, formatting issues)
........---- <--- flat surface
in this case, both heat sources cannot be distinguished from one another. both illuminate all of the heat-sensitive skin.
...........
<--- two heat sources
.........\/\/ <--- surface with pits
in this case, the two sources of radiation can be distinguished. when the left heat source is radiating, the green segments will be activated and the red ones will be in shadow. Ball pythons, with their row of 10 heat pits, can do that so well that blind snakes can find and strike a rhodent and hit it. Flatten the surface, and almost all the data is lost. its like having an eye without a lens, that only senses how bright it is in front of the head, without producing an image.
so i do think the heat pit issue is a real issue.