For the record: on Night 2, Glenn also did not bow to the Master after the duel Post 481, n2 writeup.

Fujimoto (Glenn) picked up his katana and quickly decapacitated his opponent.

The duel was over.

Shingen nodded respectfully to Fujimoto.

"Now that this has been settled, we'll go through the proceedings again."
All the other duel write-ups have the victor bowing to Shingen.