Then why in the world make Internet Widgets, Pty users create yet another login on some random .aws property that (as very best I can tell) does not support any

Then why in the world make Internet Widgets, Pty users create yet another login on some random .aws property that (as very best I can tell) does not support any kind of SSO auth that an outside organization would use: GitHub/GitLab, IAM/Cognito nor OIDC/SAML