As a (Mechanical) engineer, I would respond by saying you turn a bolt with a plastic wrench just like any other wrench, providing the moment of torsion provided by the person turning the wrench does not exceed the shear strength of the wrench material.
Using a socket wrench rather than, say, a crescent wrench means there's more nut in contact with the wrench at any given moment. So the wrench doesn't have to be quite as strong, since the torque is distributed over a larger surface area and thus a larger volume of wrench is available to absorb it.
We use some where I work. They are useful in niche applications, such as our one-off research lab equipment. They wear out slowly. They work best where we have 5 different common orifices for fluid that need to be merged into one. When they wear out, we order new ones.
We pay a tech who knows CAD and a fab house rather than a machine shop. A machine shop would probably cost a lot more. Although now that we have the design down pat, we wouldn't waste as much money on prototypes.
Our design includes 2" diameter threaded ends and it holds pretty firmly although the threads do wear out and tear off the tube with vibration and heat changes.
We've used 3D printed plastic parts in surprisingly (to us, anyway) rigorous applications. We've used printed PLA parts as prototype bearing holders on seriously high speed rotating equipment. Strength is usually close to fiber reinforced Delrin or similar plastics.
3D printing let us try and tune successive iterations for best performance far more rapidly than we could have done with classical subtractive machining. OTOH, our 3D printers care about the room temperature and HVAC breeze, whereas a lathe or mill wouldn't notice. Tradeoffs....
As an engineer my first thought when I saw what it printed was how do you turn a bolt with a plastic wrench without breaking the wrench?