Thanks for the replies thus far. I had just never seen this done before. I actually think it's kind of neat, because it's a glimpse of how things used to look, since, as Sbdcn Michael said, the sakkos is an imperial garment, not an ecclesiastical one, and bishops would've worn the phelon (as can be seen in icons of bishops that lived centuries ago).
(and, fair enough on the correction. I have seen it used in the way I did before, and so I think both are actually acceptable. I know in linguistics, we talk all the time about "alternate" forms of words, meaning a form used instead of a standard form. Still, "alternative" would've been the better word choice)