Supergiant's Hades?

Supergiant Games--developer of Bastion, Transistor, and Pyre--has a new game out, Hades.

Or at least, I think they do.

I was browsing Steam when it popped up. I really enjoyed those three previous games, so I went to buy it, but then paused when I saw the 'Early Access' label. The three previous games were story-based games, so does that mean this one is not? Or perhaps they are releasing the story in pieces?

The game is described as a "rogue-like". The early reviews all seem uniformly positive, with many saying that this is one of the most polished Early Access games they've seen.

Supergiant themselves describe Early Access this way:

We designed Hades as an Early Access game from the ground up. Our foremost goal was to see if we could create something great in partnership with our community -- a game that was true to our values about design, worldbuilding, and storytelling, and could naturally evolve based on the feedback we'd get along the way. Every aspect of the game, from its modular structure to its approach to narrative, flow from this idea.

What the hell does this mean?

If I buy Hades now, is it a beta where it changes significantly, and I would have to start over when it reaches 1.0? Or maybe because it's a rogue-like where you are constantly dying and restarting runs, changes to the core game don't really matter story-wise. And the story is set in stone, even if new chapters are released slowly?

Should I buy this game now? Should I wait for Hades to actually release? Normally, buying a Supergiant game would be a no-brainer. Buy it, play it through to the end, thoroughly enjoy it, and then wait for their next game.

Why do game companies insist on making things complicated?