I used to do that to make B&W duplicate negatives from colour negatives in one step. The result was low in contrast, so I would push it two or three stops in the E-6 First Developer to get enough contrast. AFAIR, the resulting negative had a somewhat bluish tint to it.
The reason for this was that we would receive a colour negative, and we would have to make a large production run of B&W prints in a day or two. There was usually no time to order rolls of Panalure paper (which was difficult to work with, as it required total darkness in the B&W processing area), and less trouble than making a dupe B&W negative in two steps (which was fraught with sharpness and dust issues).