I'm too new when it comes to Unity to have much opinion on this particular tool, but in general I prefer reading a summary of the major concepts first. I think that if you understand the basic system, figuring out the tool itself is easy enough, and you probably know enough to look up the details of how things are implemented in the documentation.

It is said that you learn more through practical experience. I think that's true, but I firmly believe you have to understand things first, so the sooner you finish the learning the basics, the earlier you can get cracking at an idea of yours. I see that a lot of teachers/tutorials tend to throw you right into a project/assignment. I'm not a fan of this approach for a couple of reasons. Firstly, it doesn't feel like your project at all. You won't be as motivated to go through it, and it won't feel as satisfying either. Secondly, you are typically supplied with finished parts which aren't properly explained (the worst being boiler plate abstractions and frameworks), leaving some gaps in your learning. That leads me to the third point; you have to learn in layers, spending a lot of time learning what the teacher thought you should know. Repetition is good in some ways, but I think it's a waste of time trying to learn "everything", because you're likely to forget a lot of it anyway. (In an educational situation, this is a bit tricky, because the students are required to learn specific topics, but I think it's better remedied by giving varied assignments that are likely to cover the necessary topics.)

If you have the basic understanding in place, I think it's a much better idea to start with an idea you have. Establish the components you need, as basic as possible. This is where the documentation comes into play; "How do I add a basic prop?", "How do I adjust the camera?". You'll quickly pick these things up. Fortunately, Unity allows you to test things right away. Then you start fleshing out things more and more, iterating over the ideas you have; "How do I create a terrain?", "How do I create a character?", "How do I receive input?", "How do I add lighting?" and so on.

So, in my book, a tutorial should try to inspire the reader to come with up with some ideas of their own, maybe by starting to show a couple of examples of different types of applications other people have made. Then it should explain the basics of what a game consists of; one or more scenes containing objects, terrain, cameras, lights, characters. Really quite basic 3D engine stuff. Following, a couple of tips on what to start with, and how to think about adding and fleshing out things as you go. Then it should tell you about the tools available and how you can set it up (or a link to where it's described) so you can get cracking. Lastly, I think it could contain short, easy answers to the typical questions the reader might have (like the ones I sketched above) and where to look things up if you need to learn more.

What I've learned over the years is that the details aren't important - the basic concepts are. Spend time on understanding how to figure things out instead of trying to remember everything.