Your terminology is correct, but most derailleurs are interchangeable with the pulleys. Depending on the design of the pulley, you may, or may not need to re-lube. If it actually has bearings (some Hurets do, but they're the only ones I know for sure that have them), it will pay to re-grease them, as you would with hub bearings. Otherwise, any grease you apply will likely do almost nothing.
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