פירוש על קידושין 92:6

How could the priest make such a mistake—he should know that one does not separate hallah from flour? The answer is that people know that one should not separate hallah from flour, but they might err in the reasoning. They might think that its because giving the priest dough is easier for the priest. And if the priest is okay with receiving it as flour, then the hallah separation is valid. But this is not true—this separation is not valid at all.
So the difficulty on Shmuel is resolved—if the priest keeps this flour, a problem might occur. But no problem will occur if the woman keeps the kiddushin money.