Microsoft Windows has a feature where, when shutting down, it will actually go into a state of hibernation instead of fully shutting down, to boot faster in the future. This preserves the state of the kernel and system session while locking down the Windows partition to prevent editing and corruption of data. This information can be found here.
I personally have also come across this feature when dual-booting Windows and Ubuntu and trying to access my Windows files from Ubuntu.
How does this drive locking down work? For example, does it rely on the other operating system respecting the drive lockdown (like setting a lockdown bit) or does it completely prevent the other OS from modifying the data (like drive encryption, which it clearly isn’t because the files can be read, but not written to). Can the drive be unlocked by another operating system?