Original sentence: However, unlike previous service packs, Windows 8.1 cannot be acquired via Windows Update and only accepts 8.1-specific product keys.Microsoft's support lifecycle policy treats Windows 8.1 similar to previous service packs of Windows: It is part of Windows 8's support lifecycle, and installing 8.1 is required to maintain access to support and Windows updates after January 12, 2016
Edited sentence: Although not explicitly marketed as a service pack, Microsoft's support lifecycle policy treats Windows 8.1 similar to previous service packs of Windows: It is part of Windows 8's support lifecycle, and installing 8.1 is required to maintain access to support and Windows updates after January 12, 2016