The OpenSUSE 64-bit OS type does not allow the switch to EFI firmware in the GUI.
Have you tried a guest operating system type of SUSE Enterprise Linux 15 64-bit, enabling EFI firmware in the VM's Settings and then installing? Leap 15 shares its kernel with SLES 15. Setting the OS type to SLES 15 allows Workstation to set the VM's firmware type to EFI.
The Leap 15 installer will boot with EFI firmware. It will recognize that the VM has been configured for EFI boot. By default the partitioner will configure the virtual disk as GPT, and provide partitions on /dev/sda1 for /boot/efi with vfat, /dev/sda1 for / with btrfs and a swap partition. on /dev/sda3. There are a number of btrfs subvolume operations on / to create additional mount points.
The EFI boot partition being formatted as vfat is normal, and is where the EFI firmware is configured to find the GRUB EFI bootloader from. The root partition will change from btrfs if you use the guided setup in the installer to choose another file system type (e.g. ext4) as your root .
I just verified this with Workstation 17 Pro running on Fedora Linux 39. It should work on a Windows 11 host as well.