Two-Factor Auth for Admin?

Under User Policies -> Role-based -> Administrator, the Two-factor authentication option is greyed out and set to Disabled. If selecting other roles, the 2fa option stops being greyed out and I can make a selection.

Does this mean two-factor authentication isn’t available for administrators?

If this is the case, is there a reason? Protecting the admin account seems like the most important account to protect.

Thanks,
Damon