I currently have a page with the listing as 'in-development' but it's not indexed because it's just a store page. Shameless Plug
I could probably do what you say, but I worry that people won't read the dev log and simply just download the demo and think "Wow, this sucks and it's buggy. This dev should go dunk themselves in a volcano." This is why I'm asking. Not sure how friendly the itch.io community is towards demos in progress. I'm still feel the need to bathe after reading some of the comments on Early Access stuff on Steam...
Viewing post in Uploading an unfinished demo
Users expect indie projects on Itch.io, games made by a single dev (or a small team) while they have a full time job. There’s all kinds of projects here. Although this is a personal opinion, I would say that users looking for indie games are for the most part looking for a unique experience, something creative and innovative, that would be too risky for a big company to implement. So make sure to let your creativity flow.
Steam is higher profile, with a higher bar of entry. That’s a platform AAA companies also use, so your game will sit next to other high profile games. It’s easy for a user to judge your project with AAA standards.