For a reinstall, in the storage editor, after having deleted the var/lib/machines subvolume, if one assigns mount points for the root subvolume and the EFI partition, the storage editor reports “Storage requirements not met. You must create a new file system on the root device.”
In this context, you must not create a new file system on the root device. The message means there is a root subvolume (the device), which is not empty. The easiest and safest way forward is to “Proceed with installation” and then “Reinstall Fedora”.
Deleting and recreating the root subvolume in the storage editor removes the “Reinstall Fedora” method and requires additional steps further down the installation.