I think we don't need a separate article for 8.1 when we have Windows 8 Portal. We can indicate in Windows 8 portal that it currently has SP1.
Hi, 8.1 is another OS on another kernel, so it's another product, not a SP. The Windows 8 portal will tend to phase out due to that. 8.1 follow the same kernel as 2012R2, as 8 follow 2012's kernel. Thanks !