From my experience, anything SSO-related has a steep learning curve in wrapping your head around IDP, SP, metadata, IDP-initiated vs. SP-initiated... there's a whole lexicon that isn't very intuitive. Ask me to set it up a year ago and I would have described it as "a ton of work and very complicated". Eventually it stuck, though :)

Okta client here btw, and we use SAML (2.0) for many of our SSO integrations. Okta has pretty clear support for SAML 2.0. Maybe your colleague's app is a special case?

Nope, not at all. He knew all those words and more (he is basically an oauth expert)

He said the biggest problem is how okta handles user information, roles, rights and how it is stored. He said, that they have there own idea about it. (which can be good or bad...) didn't dig deeper though :)