The host is a white box Haswell system so this is not Apple hardware. Sierra _can_ be virtualized on non-Apple PC but you'll need to use a bootloader that supports it and build a customized .iso[1] from the install medium downloaded from AppStore. I believe the same goes for Yosemite and El Capitan.

So no, it is no longer the case. It is still prohibited by the EULA though.

[1] https://github.com/kholia/OSX-KVM/blob/master/create_install...