The houses I posted photos of in that link I provided had gutters on them.
A gutter, by design, especially the newer styles, has a slightly lower fron edge, which will theoretically allow the frozen mass rize over the lip and then begin the melting process on the front side of the gutter.
Even take a look at the old 1/2 Round styles during the winter. The icicles eminate from the front side, not the rear and they are a free hanging gutter, suspended only by the strap and T-Lock bar.
I drove past the 1st house every single day on my way to and from dropping my kid off at pre-school and made a mental note of each and every possibility that needed to be explored throughout the entire winter.
It was a daily observation with no ice formed barriers precluding the Smart Vent from performing as stated. Also, the continuous heat exhaust from the Shingle Vent II Ridge Vent further enhanced the diagnosis of a properly working system, since this was installed on a cathedral/vaulted ceiling on that home.