…the phrase means:
A person suited for one job may not be suited for another job.
The practice of choosing the best person for a particular job.
Once again, the Wikipedia family (in this case Wiktionary) refers to the translation profession to illustrate usage:
The term is widely used in the foreign-language translation industry, where a translator is selected for a job not solely based on his or her fluency in the language, but also based on knowledge of the subject matter.
Related post: From GIGO to QIQO: the quest for quality
By Marian Dougan