Mixed-dimensional mathematical models for flow in fractured media have been prevalent in the modeling community for almost two decades, utilizing the explicit representation of fractures by lower-dimensional manifolds embedded in the surrounding porous media. The question of how well these models are able to represent physical realism has not yet been discussed quantitatively. For this, we draw direct qualitative and quantitative comparisons of laboratory experiments against mixed-dimensional models. Dedicated displacement experiments of steady-state laminar flow in fractured media are investigated using both high-resolution PET images as well as state-of-the-art numerical simulations.