Yes, correct behavior. false means that your Geth is up to date and is not currently syncing. It keeps importing the latest block to remain up to date. Check eth.blockNumber against a block explorer if you want to double-check.
EDIT: web3.eth.isSyncing() will also return false when syncing has not yet started (or is currently not running). If this is the case, you need to check your networking that you are connecting to peers: Why doesn't my Ethereum node have any peers?