Since the two accepted answers in English (heavy / light // hard / easy) mean distinct things (i.e. weight vs. difficulty) to English speakers, how does one distinguish here? Or are there alternative words for either situation that might be clearer with or without context?
Shouldn't this be translated more like "It is not heavy, it is light." since the opposite for heavy is light?
"It is not hard, it is easy."
"It is not heavy, it is light."
Your comment suggests that it accepted "It is not heavy, it is easy.", which would be an error and you should report it.