It will be a great idea to enable Multi-Factor Authentication (MFA) for single user or small AGOL organisations.
Forcing students, new developers, or small business to either be less secure or pay for an otherwise unused 2nd admin license is not what we expect from an industry leader that takes its users' data security seriously.
Alternatively create a free or very low cost tier admin/user management license tier that can be used specifically for this purpose.
Give back to the users that have made Esri what it is today and help them protect their data in 2022.
All the other major vendors do this (Amazon AWS, Microsoft, Google, Facebook, etc) so the only reason not to would be architecture limitations or greed.