I've been wanting Susan to wind up with an updated Nanase fairy doll since this storyline began, and I felt this was a good opportunity to make that happen.
Granted, Susan will theoritcally be summoning her own doll above all others now, but darn it, I'm the person writing this and I had an irrational desire for Susan to have a Nanase fairy doll based on Nanase's current design, SO IT HAPPENED.
Also, maybe I'm going somewhere with this, but you'll never know! Unless I am, in which case it will probably be obvious. OR WILL IT? Yes, it will. Because if such a thing happens, you will see it, and it will have been seen, which should make it be obvious.