Has Apple finally included APFS support for traditional hard drives in the latest update for macOS 10.13.1?
According to official documents and several online forums it has been confirmed that Apple is converting each and every internal HDDs into APFS File System, only when you upgrade to macOS Mojave.

APFS File System doesn't seems to create much problems in old macOS Devices with an internal HDD. So you should upgrade to the latest macOS version available i.e. macOS Mojave.