It actually is the opposite of what you say, in that the Fast Boot feature of Windows 10 is basically logging you out then hibernating the system, which is faster on HDDs but slower on SSDs (or at best the same speed of a cold boot, but at the expense of system stability in the long term since NT really likes its reboots).

It's really odd, because the first couple releases of Windows 10 were fast enough on HDDs, but post 1703 is when I started to really notice it.