Suggesting we promote the second to last bullet point to the top:

During the time it takes to configure SAML single sign-on, users won't be able to log in to your Atlassian Cloud applications. Consider scheduling a day and time for the changeover to SAML, and alerting your users in advance.

Additionally, it would be great to add something along these lines as the first or second bullet point:

Make sure you have at least one admin level account that isn't part of the domains you have verified. That way, you can still access your account if any SAML settings are incorrect.