I'm not sure I would consider this a bug per se, since it doesn't necessarily affect anything in-game, whether or not the unused locale data exists.
That being said, I do prefer the consistency of having all heat inserters with the same name/description format, so I've removed the unnecessary lines and ensured that all heat inserters use the same localised format (except for the long-handed heat inserter; because I don't like the name "Heat Long-handed inserter" that it would be otherwise)
As a minor aside, I also fixed the base heat-inserter icon to use the same format as the other heat-inserters, for consistency as well. Implemented both changes in v1.2.4