You and I are on the same page with regard to Fast Startup. The incident I encountered in 2015 under Windows 8 was enough to make me say, "never again."
The increase in startup speed is negligible with a HDD and pretty much invisible if you're using an SSD with Fast Startup enabled. I would rather know that when I shut down my system it is shut down and will reload afresh when powered on again. Others feel differently, but it is important that they be aware of the potential issues and if they choose to use Fast Startup to know that using Restart will force the machine to shut down entirely and load Windows afresh from the drive.
I've seen plenty of other instances where simply turning off Fast Startup has cured an ongoing issue where the user never did a Restart. That also tells me that it's just not worth it.
Brian - Windows 10 Home, 64-Bit, Version 1803, Build 17134
A great deal of intelligence can be invested in ignorance when the need for illusion is deep.
~ Saul Bellow, To Jerusalem and Back