I think the problem is that the dev will promise the update at a certain time, and then miss the deadline and struggle to communicate after that.with a branching system that gets more complicated as the updates add up, things will become more difficult to troubleshoot at this point, especially if the dev team is really just one guy.
as for cancelling subs, many other patrons of other devs usually just sub on the month when the update drops and unsub soon after. iirc, patreon's model is really akin to those Renaissance patrons who can afford to pay monthly the artists in their employ. the patreon model of ordinary guys pitching in monthly for another ordinary guy's dream project is really only something that is very post-2010-ish.
as for the radio silence, while it might suck for customers, it's usually the better way for games development to happen, rather than communicate too much to the audience. the "we hear you" mentality if many indie and AAA development teams usually are their own can of worms.
The better option would be to just not communicate the specific time of the update, instead maybe giving an estimate at most with some leeway time. Like in the next month or so sort of thing.
They're causing problems because they're promising specific times and never meeting them. And then the excuses given are always just..
Maybe the hope is that it inspires people to resubscribe before the update in preparation, but when you're constantly missing the update time, it puts more people off.
But I agree, patreon's monthly subscription is obviously not good for game developments like this. It would be better if they introduced a new style of membership for games in particular. You could still keep a monthly subscription, but instead, prompt developers to do lower monthly subscriptions to then give discounts to unlock updates, but leave it open that people could pay to access the update at a different price without subscriptions.