BTW, if you watch it yourself, you have a nice case of how a user discovering the interface reacts, where he does/does not get how it works etc 🙂
Also, at the end of the video, Tim explains that in Acy5 he always "convert the Tags" before sending, otherwise the newsletters visible also in the front-end always display dynamically the "last X articles" (and not the situation at the sending day/time).
And apparently this is not possible anymore in Acy6 or he does not see how to do it.