Yes, I understand. Not liking the style of teaching is certainly a good reason for transfer. However the admissions people think differently. They have so many applicants, they want to admit transfers who have a really solid reason.
There are bad teachers everywhere, and so its not a guarantee that you will be satisfied if they admit you as a transfer. It almost paints you as unhappy and ungrateful at WashU. You certainly don’t want to disparage or paint WashU in a bad light. I would seriously consider framing your argument in a different light. Instead of focusing on teaching style, perhaps the upper level math courses are not what you want? Perhaps you want to do a bachelors thesis, or have an option to graduate with honors classes. Or even the ability to take electives in another (related) department. These types of arguments would be far better IMHO.