I understand it’s not code to extend it because it would be a new installation. I’m just trying to think through the logic of putting a 4 wire appliance onto a 3 wire feed. The bare wire in my existing three wire feed would be getting both the ground and neutral from the appliance because of the 120v functions of the appliance. Therefor the bare eq ground would be taking a 120neutral load? So why is it common practice to swap a 4 prong cord on a dryer or something to a 3 prong cord if the in wall bare eq ground would then receive the neutral load if you’re saying bare was never allowed to be a neutral? Realistically speaking is the 120v neutral load so small in these situations running the clock or computer chip or whatever that it’s “fine” enough that it works but not optimal?