Interesting. If you are able to make it so only followers would see it and nobody else, how would it inflate follower count? My original intention is the opposite, to not get followers. Patreon allows pausing your account to not get new subscribers. Twitter allows private accounts, again to stop getting followers. Both could be set indefinitely.
Also, it isn’t for sale, it’s to be given for free to followers.
how would it inflate follower count
If you make something exclusive behind a prerequisite, that prerequisite is obviously needed to get the exclusive thing. For paid content, that prerequisite is the payment.
For free content, the cost would be giving the developer your user name and to get the developer's activites in your feed, which can be seen as subscribing to a newsletter. And the gain for the developer would be visible popularity. The follower counter.
On a site like GameJolt you can directly see how they value this. They only allow new developers that have a follower count of 1000+ on social media.
So to answer the question: it would inflate follower count, because people would have an incentive to follow. Without being a follower, you cannot get the content.
Patreon introduced something like that. Previously, any "follower" would be people that subscribed, and that included payment. But since a while ago, you can subscribe to a creator and the creator can make posts that are "free", but exclusive to subscribers. Having more subscribers, even free ones, makes a creator look more popular. But you still subscribe to the mailing list, in other words, you agree to get advertisement from the creator.
Anyway, as I said before, you do not even need to have an account to use Itch. Using the follower mechanic for any kind of mechanic for distribution does not fit in with that design.
It is practically certain, that you have silent followers. People that put your game in a bookmark. Or a private Itch collection. And probably some people that gave you money on Itch, but do not have an Itch account and cannot follow.
If you just wish to quietly give your followers content, but not block non-followers, just use a devlog or even a regular update. Your followers will get a notification. You could make an unlisted project and link to it from a devlog. But blocking non-followers is not something that Itch has any easy mechanics for, except payment.
