It's a bit of both and also neither/nor :-) I do have lots of experience with those tools in the field, but also because I did lots of research beforehand. However, the reason why I chose these tools is actually because of some specific features that made them perfect for the book:
1. Gulp's task system is super-easy to grasp, because it's as easy as defining a function. And once you get the knack of streams and plugins, you can actually execute anything within a Gulp task. Even though there are lots of other build tools out there that are better suited for other use cases (like Webpack for React), Gulp is still the only tool where you Make-like freedom without the overhead of other tools or the opacity of others.
2. Bower is the only dependency manager that features a true flat dependency tree. This is crucial for front-end development, especially if you want to cover a broad area of use cases and not just stick to the MVC framework of the month. Also, you can easily create your own dependencies without having it to publish to certain registries.
3. Yeoman has as scaffolding tool the best range of pre-defined generators and is also the only one that's easy to extend. I know no other tool that's on par with Yeoman in terms of accessibility for new developers.
That being said, all three concepts of build system, dependency manager and scaffolding tool are explained in a way so you can easily switch the tool for one that's better suited for your purpose. Want to drop Bower in favour of NPM, so worries. All concepts and everything you've learned so far still applies. Finding a better scaffolding tool: The stages of input, assembling and installing still hold up. I also highly suggest that if the eco-system you are working in has other tools for those use-cases that are more common, please use them. The Ember-CLI for instance has all those features of building, dependency management and scaffolding already in place. It would be crazy recreating everything with the tools I've chosen to explain the core concepts. However, the concepts are still the same. So
you should be able to understand the process of Ember-CLI nonetheless.
Never forget the longevity of JavaScript projects ;-)