They do. If you have the wedge product as an assignment of some member of the (nth) exterior product over the cotangent bundle to each point on your space ($\mathbb{R}^n$ or whatever it may be), then something like $xdy\wedge ydz$ is just a representation of this assignment which just so happens can be represented by the exactly same expression everywhere. The form is just a fixed function at any given point in the space, $x,y,z$ etc are not changing and so act exactly the same as constants in the written expression.
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