On windows, preallocation=full qcow2 not creatable, qcow2 not resizable
Description of problem:
Not possible to create a fixed-virtual-disk qcow as one may do on linux.
One sometimes may want to create a fixed size qcow2, as can be done with the fixed variants of VHDX, VMDK, VDI, 

The advantage of a fixed virtual-disk format, such as fixed-VHDX, fixed-VMDK, fixed-VDI is that it keeps the disk-meta-data as a header bundled along with that is essentially a raw image, allowing for seamless tooling and management of virtual-disks

Workaround use a raw file as diskimage. (see workaround given below)

To be very general, the implementation of this may need to factor in what underlying operations (fallocate, fallocate_punchhole, truncate, sparse) are supported by what filesystems (NTFS, ExFAT, ext4), choice of filesystem-driver (sometimes the driver may not have yet implemented an underlying operation), and operating systems (Linux/Win), and possible workarounds to achieve the same effect in the absence of underlying-operation.
Steps to reproduce:
1. open command shell
2. run the qemu-img command. In my case, qcow2 file is attempted to be created on a drive with ExFAT filesystem.
Additional information: