Looks like a really poor pitch. It should be taut and not saggy like the one in the video. I've seen a couple of the z pack tents in the flesh and they are really nice but not my choice for UK weather. For sure the guys I was with didn't have those issues and they either got them dry by leaving the door open while having breakfast or gave it a quick wipe.
Would be a fairer and more objective test if the person had been more competent.
You can be the most competent camper in the world, you will never be able to stop condensation in a single wall tent, especially ones made of DCM, like the Zpacks tents...It may be waterproof, but it isn't exactly breathable, so without leaving the door or doors open a bit, even in the rain, there is nowhere for moisture in your breath to go except onto the inner surface of the tent wall.
The driest tents are two wall tents which have an inner tent that is mostly made of no see-um mesh.
The mesh is highly breathable, allowing moisture to pass through and be carried away by the slight draught that the design sets up between the inner and outer walls, before it has time to condense on the inside of the rain fly.
Most of the best new tent designs utilise mesh inner's as it is the most effective method to stop condensation. Two wall tents are heavier though, so it comes down to whether you prefer to carry a lighter base weight or being able to enjoy a dry nights sleep.