I completely agree, but the fact is that they are doing a lot of the exact same things with 1.1 that they did with the beta. They are saying some stuff but ultimately keeping the community in the dark through the entire dev process. I mean I am not saying that this is necessarily a bad thing, but it is ultimately unnecessary. Since release, they have put out both full release updates and pre-release updates. Honestly, I think if they put out a pre-release ("beta") patch out with all the current changes even without full testing, the community would be much better off. Modders would be able to have their mods ready for patch release instead of having to wait and see what breaks and regular players would be able to try the changes and give good honest feedback. Since they would be pre-release, only those players who go out of their way to get the raw patch would play them and you wouldn't have this up in arms situation at all since the community would have plenty of time to discuss the actual changes. Right now, all the community can do is debate about the small tidbits of information given in this post or that with most of the conversation revolving around how one believes the system works instead of how it does.
Regarding the modder stuff, I disagree with you. Since literally anything can change between beta and non-beta of a patch, the time in between will not help me at all as a modder. For example, for the Elves mod, I have to copy xml for every building, every armorpiece, every tech (and the techtree), every weapon, every piece of clothing, every hairpiece, every accessory, make sure quest items can be worn, mounts ridden and so on. And that's one faction. I'm going to have to do the same thing with the Drota. There's no point doing all that work, which takes hours, just to have a mod invalidated a week later because 10-15 values changed.
Only very small mods can be updated to a beta patch and then not require further updates when the beta turns into non-beta.
Beta periods will probably be known as mod-less periods (for those that choose to test the beta).
This is all assuming there have been no changes to the structure of XML, or changes to how mods work. Nothing has been announced, so far. This is where I think a beta period may come in handy for modders, in the sense that we can see what has changed in the xml structure between old and beta versions. Then, when we are handed the appropriate XML at non-beta release, we know how to go about things efficiently.