Good point - I wonder what sort of crowd the horrendously elusive FATEs like the Behemoth, Proto Ultima and part 3 of Coeurlregina would bring in? And more people would be able to participate even if they're not up to the end of Stormblood yet.
That's the idea, yes. Testing to see what happens when everyone rushes to a specific world for some reason, and how the servers handle it - or at what point they can't.