Amazon Cognito?

I’m tasked with building the IdP for a service hosted in amazon. The team working on the service side has told me that Amazon doesn’t support true a Idp-initated flow. They’re asking me to do something they’re calling “IdP Emulation” or “IdP Simulation” which is where I build the service URL myself and hit it directly bypassing two steps in the typical SAML flow. Anyone heard of this before? Anyone else written an IdP for a service in amazon?

My understanding is that Cognito does support IdP-initiated SSO.

The example URL they list is for ADFS as the IdP when using IdP-initiated SSO.