So I got my backer early access/release key and GOG is still saying 4 more days until release. Anyone have any idea if this will change and adopt the early release model mentioned by the devs?

Same issue here!

Just found out we can actually download the game!

You just need to change the beta channel to "early access".
In Gog Galaxy, on the game's page : Manage Installation -> Configure -> Beta Channels

Thank you very much, it works!

If someone need more details, assuming you already entered your redeem code :
- Launch Gog Galaxy
- Go to the Eiyuden page in your game
- In the parameter (top right button) : "Manage Installation" -> "Configure" -> "Beta Channel" -> "Early access" as Twilightsblue said.
- The password is your digital code

Oh cool. Thank you

That's because there are 2 different early access times, one started in the 18 of April for Kickstarter backers
The Pre-order one starts tomorrow, if you pre-order you have to wait till tomorrow.

That is what got me confused. Thank you for clarifying the 2 different EA.