Or it could do more good than harm...
The pros and cons of supplemental heat shift and vary based on individual setup variables, and should not be thought of as an absolute... Almost all commercial chicken farms provide supplemental heating and they don't do it because it harms their flocks, quite the opposite...
In general for the small backyard chicken keeper, with healthy cold tolerant birds, in a well ventilated and draft fee coop the cons of supplemental heat generally outweigh the pros, but that is not a one size fits all answer...