Work or School Account required when sharing with hotmail/ personal account?

It sure isn't very clear, is it?

Further down that page, it says:

• Guest users using social identities will experience more limitations because of sign-in restrictions.

  • They can use consumption experiences in the Power BI service through a web browser
  • They can't use the Power BI Mobile apps
  • They won't be able to sign in where a work or school account is required

It does seem like it should be possible though. The detailed documentation here says this:

Can I invite guest users with consumer email accounts?

Inviting guest users with consumer email accounts is supported in Power BI. This includes domains such as hotmail.com, outlook.com and gmail.com. However, those users may experience limitations beyond what users with work or school accounts encounter.

It seems like Microsoft has been making some authentication changes recently but isn't very clear where they apply. When is a "work or school account required"? I'm confused now too.

The Customer Support Team can hopefully provide a better answer.