I bought a torque wrench for my RadCity 5. I've had a mountain bike for over 20 years for which I never used a torque wrench, but then again that thing was built like a tank. I think Rad's instructional videos and guides are HIGHLY "liability" sensitive. I think it is perfectly possible to assemble the bike (which comes mostly assembled anyway) without a torque wrench and be perfectly safe. But I don't know this bike and this manufacturer.
For one, their quality control appears to be a bit lacking. When I received the bike, I found that one of the fender mount brackets (which need two drilled holes on each) had only one hole drilled on it rather than two! The other one was just fine. How does THAT happen??? Fortunately, I live in Seattle, and I could just hop on over to the Seattle store and they got me a non-defective one, and helped me to take out a couple of hex bolts (on the head tube for the front rack) that I foolishly stripped. They were perfectly nice. But I suspect that the manufacturing and shipping part of their company lacks adequate quality control, given the fact that the back fender comes mounted on the wrong (upper as opposed to the lower) holes on the fender as it is supposed to be, and this is a systemic problem, not just mine... I want to be on the safe side and follow their instructions to the letter in case something goes sideways.
And also, the ebike's target consumers appear to be older folks some of whom had little experience riding or maintaining a regular bike. Rad probably wants to make sure that they provide as accurate and safe instructions to them as possible in case something goes wrong so that they can say, "hey, we did everything we could to provide a safe instruction."
Even though I feel fairly comfortable maintaining a regular bike, I felt that this whole ebike thing is a qualitatively different experience, and I wanted to do it right. And torque wrenches are a pretty cool thing to own.