Where do they say that?
SSO -> token that works only for specific role, where the specific user is supposed to be able to take many roles, is very hard to do with OIDC unless you can mangle OIDC tokens properly, whereas it's way simpler to do with SAML
Whatever you've described sounds more like internal problems / challenges of their own implementations than anything else... especially the OpenID Connect as a delegated authentication protocol itself.
If we look a bit closer, we notice that the first four use OpenID Connect under the hood. These names are fancy names for OpenID Connect with a little bit of something extra on top from Apple, Google, and so forth.