Coaching your guest users through the External Sharing Experience.

Hi EricDavisTech, thanks for your comment.  

I understand that all these different channels for invitations can be frustrating; but it helps, I think, or at least it helps me, to keep the sheer breadth of Office 365 and SharePoint Online, and not only in the number of tenants (millions) or the number of users (tens of millions), or even the breadth of size (from single user tenancies to hundred thousand seat behemoths), but also the magnitude of different businesses and organizations, in every single industry, in education, health care, government, tourism, services, manufacturing, research and engineering, to non profits and charitable work; Office 365 is the largest enterprise cloud in the world.  And so we approach things like external users the way a mechanic approaches any other tool.  Is it absolutely necessary to have 4 or 5 different ways to invite a guest user?  Probably not, if you're talking about a single tenant, or even a handful of tenants.  But each method was introduced because it was vitally important for a number of customers in that vast ecosystem.  Simpler is preferable to complexity, you are absolutely right.  But as the creator of tooling, we have to make sure the right tool lands in the right hand for the right job.  And that's what we're trying to do here, provide you with the correct tools, and help give you the best information to empower you to make the right decision on which tools you'll need to employ.  If all you work is on your personal car, you probably don't need multiple thousand piece ratchet sets in order to work on your car.  But if you are supplying tools to all the mechanics working on all the cars across the world, it makes sense that you want to have the right tool for the right job and get it to the right person.

Again, I'm not denying the frustration that can accompany the size and scope of the tooling that is just SharePoint Online, let alone the entire Office365 suite!  I just wanted to highlight some of the broader influences on why such a huge ecosystem requires a certain level of complexity.

On a personal note, thank you for mentioning invitations to Unified Groups.  I'll work on that this week and update the document.  I apologize for the oversight.