In my understanding, this delegated signing approach is viable technically, but there were questions as to whether the model would end up putting too much strain on individual relays if more users adopted this method of authentication. Have to defer to npub1tv8gmfhalwnxxquxjzeh6gtdsdz6vg7vx0s3rt7s7uuw6aujh32qn77wn2 and others who have deeper technical knowledge on this.