If I hit somebody else on my bike… I don’t think I have insurance for that liability? I don’t think my auto or homeowner’s insurance policy mentions me riding bikes at all, let alone an exclusion for DIY e-bikes.
The problem is (IMO) e-bikes that are more "motorcycle" than "bicycle". Which includes a massive number of the kits.
There currently is no national framework for classifying e-bikes. There's the 3 tier system that some industry groups use, but it directly conflicts with most state's moped/motorcycle regulations.
Safe bet for an e-bike is a "class 1" bike from a major brand. 20mph cap, no throttle, the most "bicycle" of the 3.
Class 2 bikes keep the 20mph cap, but add a throttle (don't need to pedal). This probably makes it a moped or small (50cc) scooter in some states.
Class 3 removes the throttle, but bumps the top speed to 28mph. Again, this speed probably makes it a moped or scooter (or possibly even a full motorcycle).
And then there's the e-bikes that are more motorcycle than bike. 30+mph, powerful engines, and the pedals are truly vestigial. Supe73 and Surron bikes fall in this category.
Pedaled vs throttle is an ablest issues; not everyone has picked up on this.
I’m ambivalent about throttles - much more concerned about the mass and speed of some e-bike when they inevitably get used on sidewalks, multi-use paths, etc.
And if you don’t think you have liability coverage, that’s exactly the risk. If your policy doesn’t mention bikes, it’s more likely not covered than automatically included. The more you do things outside the norm—like DIY e-bikes—the higher the chance standard policies don’t cover it.
Not saying you’re wrong, just that it’s worth checking so you don’t get caught off guard.