[the phantom]

But Lottie, it paves the way for him to continue serving a purpose once in Mandos. He's already assured his death in one fashion or another, and now the only missing component is having an angle to work after death. Now we see what it is.

Plus there's always the remote hope that there will be a counter-reveal, particularly if the true Seer is also on the chopping block and is put forward as a suitable replacement candidate. A Cobbler would be foolish to ignore that glorious possibility.