Test area's are for people who wish to help with the debugging process, or need to see the new content, or both.

Not everyone wants to help, so you keep a more or stable version for everyone else to play on.

Its also a good idea to have a test version in case your new update breaks the game completely.

Since players can post reviews even during Early Access I think most developers try and keep the game largely playable.

Releasing a huge patch with potentially massive bugs would invite a lot of review bombing so devs create EXTRA EARLY ACCESS branches to test stuff out before hand.

Basically, people expect Early Access games to be completely playable and will throw a ♥♥♥♥ fit if it isn't so devs are forced to do stuff like this.

Originally posted by Honorable_D:

Since players can post reviews even during Early Access I think most developers try and keep the game largely playable.

Releasing a huge patch with potentially massive bugs would invite a lot of review bombing so devs create EXTRA EARLY ACCESS branches to test stuff out before hand.

Basically, people expect Early Access games to be completely playable and will throw a ♥♥♥♥ fit if it isn't so devs are forced to do stuff like this.

Didn't think of that. Good point!