Sam, I know you have it in for the Arizal, but this time, although he agreed to it, the Minhag of using a white one is from the Maharil. As to the issue of this resembling the Gemara’s case of Darkei Emori, I’m sure you are aware of the answers given. Some say to take the white one without specifically asking for it, since the Gemara only mentioned asking for it.
This might sounds like a poor excuse but the same answer is given to explain the Sefer Chasidim in the topic of Tarnegol Shakara Ketarnegoles. The Chida, I think, explains Eshta Ve’osir this way, too. The Gemara is actually Meduyak this way, since it switches from one who does this or that to one who says this or that.
Besides for this, I personally don’t get the big deal. You aren’t asking for a white chicken for some mysterious reason. You want a white one just for a Remez.
And to answer the big Pliah on the Chareidim, we are Makpid on not trying to be smarter than our Rabbeim.