Those are no longer in the installer.
If wanting to create a bootable installer/thumbdrive, just need to run the command for Big Sur:
You can use a USB flash drive or other secondary volume as a startup disk from which to install the Mac operating system. These steps are primarily for system administrators and other experienced users.
support.apple.com
Code:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
Any instructions that need BaseSystem, InstallESD are out-dated.