This is a great point. Bombadil _is_ also tied to the DOM much like those tools, but as you focus on providing just a set of generators (which can be largely the defaults already supplied by Bombadil), you get a lot of testing from a small spec. You might need to specify some parts in terms of DOM selectors and such, and that has coupling, but I think the power-to-weight ratio is a lot better because of PBT.