Why is the consistency cost taken between cons_logits of student and class_logits of teacher?

[Nitinsiwach]

I am talking about
self.mean_cons_cost_mt, self.cons_costs_mt = consistency_costs( self.cons_logits_1, self.class_logits_ema, self.cons_coefficient, consistency_mask, self.hyper['consistency_trust'])
What is the difference between using 'self.class_logits_ema' and using 'self.cons_logits_ema' as consistency targets?