It's not "so obvious" to me. Please explain. No exposed metal is in contact with the conductor teeth.
It is not something that I would ever think of doing live, no matter what the instructions may or may not say. I can't imagine any of the safety departments in the plants I have worked in permitting me to do that where the run conductor is live.
I agree with you on the self piercing tap thing. Still some risk of "making the circuit" into a fault but if we doing this live we kind of assume effort was made to assure there is no current going to flow when connection is made.
Aside from the safety for people working on this which I think is the most important aspect, maybe should also ask those that want it done live if they are willing to have possible downtime should something go wrong? Wouldn't be planned downtime here if something goes wrong where a planned shut down at least has some control to it which may be better for whatever this supplies.
If I were in the OP's position, I may or may not do as you suggest. I'd have to look the situation over especially looking to see if everything is finger safe in the area of the tap. But to answer your question, unless the load is purely resistive, the load would contribute to the arc flash if things go wrong.
I line breaker not so bad. At least you are not directly contacting anything live. I don't like to but occasionally have installed NF (bolt on) breakers on live bus.
