No, if you take money and let them play the game it needs to have a decent level of gameplay, even if it isn't fully fleshed out.
For instance, Rust is an early alpha access game, but it's already pretty amazing and people have 100's of hours in it. And there's a long way to go on features to add. If the game is a shooter and just has a basic SP terrorist hunt on a map or two, that's not ready to offer anyone.
I doubt we're at risk of that since GB has been in the works around 6-7 years, but yes, if you're taking money and people receive a game for that money it IS expected to not just be a POS you can't do anything with for the near future.
This isn't an investment, it's a purchase.
All that opinion aside, I see this as a positive thing and a better way to go than Kickstarter. With people playing an alpha that means there's actually something there. People can check with players and youtube for the current status of the game and jump in when it reaches the level they find ok. Today I checked out Kenshi. It was out months ago with early alpha access that was IMO far from ready for even that. So I didn't get it. It didn't even have sound. LOL Now, it looks pretty far along compared to that so it was worth it and I picked it up.
No mystery like with Kickstarter, so I see this as a positive development for GB.
And I wish them the best of luck, I look forward to seeing the game.