For the sake of clarification: Fast Boot and Fast Startup are not the same thing.
Fast Boot (BIOS option)
Fast Boot is a BIOS option which (if present, and enabled) allows certain self-tests to be skipped during pre-boot (before handoff to a bootloader). Fast Boot settings may exist in varying locations, or not exist at all; as every BIOS has differing capabilities.
Misinformation in Internet search results may lead to a belief that Fast Boot (the BIOS option) and Fast Startup (hibernation) are the same; they are not:
It is generally recommended (but not compulsory) to disable Fast Boot when using Linux either standalone or in a multiboot scenario.
Fast Startup (Windows)
Fast Startup is a hibernation variant which might be enabled by default on some Windows computers.
With Fast Startup enabled, Windows does not actually shut down; instead, it sleeps. When the computer subsequently wakes from the hibernation state, this gives the illusion of a faster startup and shutdown experience.
When multibooting, this can cause havoc with boot processes, and NTFS mounting functionality, in Linux. To better understand these issues, and their consequences, please see the related article [Primer] NTFS on Linux.
Fast Startup must be disabled in a multiboot scenario. 
There are many documented ways to turn off fast startup in both Windows 10 and 11, however, the easiest is to use the following command – from an administrative command prompt – this will disable all hibernation (other sleep states will not be affected):
powercfg /h off