It's a patreon-type account. You pay money because you want to support the author.
He in return shows the supporter what his money goes towards before the public as an exclusive thanks for supporting him. It's really not that complicated.
During the development of Smashboy when he had no ci-en account yet, there was absolutely no information about the game before it received its page on DLSite. So with his ci-en account and the status updates you got far more information than you got about Smashboy last year.
And before you say well maybe you would've gotten the public demo if it wasn't for his backers:
The trial you receive as a backer is not very fit for public release. It has a lot of little bugs, glitches and unfinished touches that would make a bad impression.
If a dev doesn't give me the time of day before expecting me to open my wallet, I'm not going to consider doing so.
I'd be happy to support excessm because I absolutely love their games, but that every single speck of information is behind a paywall turns me off completely. And backers aren't even allowed to talk about it. Why so hush-hush?
What literally every other dev does, is that they put notes and maybe pics on the free part of their post, and then things like gameplay videos, animations, demos etc go behind the paying part.
To me, that is a perfectly acceptable system that earns my moolah, and I have supported devs that have done this.
Because I like what has been shown!
If there's no information down at all I have no idea how far something is in development, and I have no idea what I'm getting for my money. So why should I be expected to? Just because I like a dev doesn't mean I should throw money at them and hope for the best, right?
I mean, look how well that works with pre-ordering games...