3) The internal drives of Macs are automatically converted from Mac OS Extended (HFS Plus) to Apple File System (APFS) when upgrading to macOS 10.14 Mojave.

What file system does macOS use?

Mac OS X supports a handful of common file systems—HFS+, FAT32, and exFAT, with read-only support for NTFS. It can do this because the file systems are supported by the OS X kernel. Formats such as Ext3 for Linux systems are not readable, and NTFS can’t be written to.

Does macOS Mojave require Apfs?

APFS in Mojave works fine on all regular storage media

When you install Mojave onto an SSD, hard disk, or Fusion Drive, if that is still in Apple Extended (HFS+) format, the installer will try to convert that storage to use APFS. There is no option for it to do otherwise.