Manage identity centrally is probably referring to using an identity management system like Okta, Microsoft Identity, or hosting your own IdP and using strong hardware 2FA. You don't want people creating their own accounts manually for everything or shared accounts that everyone knows the password for (or is on a shared spreadsheet that the entire company has access to).

At this point most startups would just use Google; since they're almost certainly using Google as their email provider, and "company email" is a de facto root-of-trust even if you don't intend it to be, there isn't really a whole lot of thought that needs to go into it. It helps that they have the best 2FA stack of any mainstream cloud service.