Hmm, remember that if these JPEGs are already in your LR catalog, then moving them in the Finder will cause LR to (temporarily) not be able to find them. You'd have to guide LR to the new directory where the JPEGs reside. If you're just copying them, then no problem.
Keep in mind that LR isn't a tool for organizing your images "on disk". It's more of a tool for organizing images via metadata or other structures -- keywords, labels, collections, etc. -- to help you find them more easily later on. File copying and moving operations don't really fall under the LR umbrella.