“Notion, Slack, all these systems, when you log in via SAML they use your email address as your primary identifier.”
One work email change broke Notion, Slack and Datadog, and fixing Notion meant temporarily restoring her deadname address. SAML already hands every app a stable NameID for exactly this case. Jira used it and handled the change with no fuss. When Jira is the only app that gets it right, the rest of the industry has no excuse.