The answer to your specific question about 働 hataraku is a no also. The onyomi was based on the right half of the character which is Chinese. Chinese 勞動 vs Japanese 労働. The Japanese character 働 is never used in Chinese. Do a search in Google and specify this character and restrict the result to Chinese pages only. You will some webpages using this character, but they are mostly Japanese pages mislabeled as Chinese pages. They are some Chinese pages using this character in the context of referring to the Japanese Labor ministry. I don't count that as reverse importation. IMHO, the statement in the article about reverse importation is incorrect.