Install Win 10/11 HWID Key

You can find this option in MAS extras section.
HWID (Digital License) can auto-activate a system even after OS is re-installed.
But this auto-activation works only when HWID (Retail/OEM/MAK) key is already installed which happens if you downloaded Windows 10-11 for free from the Official Microsoft website.
However, Business versions (Windows Enterprise, LTSB/C editions) are not publicly available. These editions have the KMS key installed by default. Due to this HWID can't auto-activate the system.
To avoid running the HWID script again, you can instead just install the HWID key and the system will auto-activate.
This is the scenario where this option is useful.