That's certainly important to note. Though in this case the game is done already and basically "release" quality. I think they did the same thing for TIS-100 as well; Early Access for a bit even though the game is done and 99% bug-free.
They've been releasing games this way for a while. Early Access with most of the pieces in place, with some polish on graphics, balance, and music for a few months before it's all finalized. Shenzhen I/O and Opus Magnum were done that way for sure.